diff --git a/R/RcppExports.R b/R/RcppExports.R
index 206ece8..b3a2530 100644
--- a/R/RcppExports.R
+++ b/R/RcppExports.R
@@ -1,12 +1,12 @@
 # Generated by using Rcpp::compileAttributes() -> do not edit by hand
 # Generator token: 10BE3573-1514-4C36-9D1C-5A225CD40393
 
-rcpp_colour_values_hex <- function(x, palette, alpha, na_colour = "#808080", include_alpha = TRUE, format = FALSE, format_type = "numeric", digits = 2L, summary = FALSE, n_summaries = 0L) {
-    .Call(`_colourvalues_rcpp_colour_values_hex`, x, palette, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries)
+rcpp_colour_values_hex <- function(x, palette, alpha, na_colour = "#808080", include_alpha = TRUE, format = FALSE, digits = 2L, summary = FALSE, n_summaries = 0L) {
+    .Call(`_colourvalues_rcpp_colour_values_hex`, x, palette, alpha, na_colour, include_alpha, format, digits, summary, n_summaries)
 }
 
-rcpp_colour_values_rgb <- function(x, palette, alpha, na_colour = "#808080", include_alpha = TRUE, format = FALSE, format_type = "numeric", digits = 2L, summary = FALSE, n_summaries = 0L) {
-    .Call(`_colourvalues_rcpp_colour_values_rgb`, x, palette, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries)
+rcpp_colour_values_rgb <- function(x, palette, alpha, na_colour = "#808080", include_alpha = TRUE, format = FALSE, digits = 2L, summary = FALSE, n_summaries = 0L) {
+    .Call(`_colourvalues_rcpp_colour_values_rgb`, x, palette, alpha, na_colour, include_alpha, format, digits, summary, n_summaries)
 }
 
 rcpp_convert_hex_to_rgb <- function(hex_strings) {
@@ -21,12 +21,20 @@ rcpp_convert_rgb_vec_to_hex <- function(rgb) {
     .Call(`_colourvalues_rcpp_convert_rgb_vec_to_hex`, rgb)
 }
 
+rcpp_get_format_type <- function(palette_type) {
+    .Call(`_colourvalues_rcpp_get_format_type`, palette_type)
+}
+
+rcpp_get_r_class <- function(obj) {
+    .Call(`_colourvalues_rcpp_get_r_class`, obj)
+}
+
 rcpp_vector_type <- function(new_type, existing_type) {
     .Call(`_colourvalues_rcpp_vector_type`, new_type, existing_type)
 }
 
-rcpp_list_size <- function(lst, total_size, existing_type) {
-    .Call(`_colourvalues_rcpp_list_size`, lst, total_size, existing_type)
+rcpp_list_size <- function(lst, total_size, existing_type, format_type) {
+    .Call(`_colourvalues_rcpp_list_size`, lst, total_size, existing_type, format_type)
 }
 
 rcpp_refil_list <- function(lst_sizes, colours, vector_position) {
diff --git a/R/colour_values_hex.R b/R/colour_values_hex.R
index 0513328..988c061 100644
--- a/R/colour_values_hex.R
+++ b/R/colour_values_hex.R
@@ -147,7 +147,6 @@ colour_values_to_hex.Date <-  function( x, palette, alpha, na_colour, include_al
     , include_alpha = include_alpha
     , n_summaries = n_summaries
     , format = format
-    , format_type = "Date"
     , digits = 0
   )
 }
@@ -165,7 +164,6 @@ colour_values_to_hex.POSIXct <-  function( x, palette, alpha, na_colour, include
     , include_alpha = include_alpha
     , n_summaries = n_summaries
     , format = format
-    , format_type = "POSIXct"
     , digits = 0
     )
 }
@@ -182,7 +180,6 @@ colour_values_to_hex.POSIXlt <-  function( x, palette, na_colour, alpha, include
     , include_alpha = include_alpha
     , n_summaries = n_summaries
     , format = format
-    , format_type = "POSIXct"
     , digits = 0
   )
 }
@@ -196,7 +193,6 @@ colour_values_to_hex.default <- function(
   na_colour,
   include_alpha,
   format = TRUE,
-  format_type = "numeric",
   digits = 2,
   summary = FALSE,
   n_summaries = 0
@@ -213,7 +209,6 @@ colour_values_to_hex.default <- function(
     , na_colour = na_colour
     , include_alpha = include_alpha
     , format = format
-    , format_type = format_type
     , digits = digits
     , summary = summary
     , n_summaries = n_summaries
diff --git a/R/colour_values_rgb.R b/R/colour_values_rgb.R
index 6bb0bcf..b2d5371 100644
--- a/R/colour_values_rgb.R
+++ b/R/colour_values_rgb.R
@@ -106,7 +106,6 @@ colour_values_to_rgb.Date <-  function( x, palette, alpha, na_colour, include_al
     , include_alpha = include_alpha
     , n_summaries = n_summaries
     , format = format
-    , format_type = "Date"
     , digits = 0
   )
 }
@@ -124,7 +123,6 @@ colour_values_to_rgb.POSIXct <-  function( x, palette, alpha, na_colour, include
     , include_alpha = include_alpha
     , n_summaries = n_summaries
     , format = format
-    , format_type = "POSIXct"
     , digits = 0
   )
 }
@@ -141,7 +139,6 @@ colour_values_to_rgb.POSIXlt <-  function( x, palette, na_colour, alpha, include
     , include_alpha = include_alpha
     , n_summaries = n_summaries
     , format = format
-    , format_type = "POSIXct"
     , digits = 0
   )
 }
@@ -155,7 +152,6 @@ colour_values_to_rgb.default <- function(
   na_colour,
   include_alpha,
   format = TRUE,
-  format_type = "numeric",
   digits = 2,
   summary = FALSE,
   n_summaries = 0
@@ -172,7 +168,6 @@ colour_values_to_rgb.default <- function(
     , na_colour = na_colour
     , include_alpha = include_alpha
     , format = format
-    , format_type = format_type
     , digits = digits
     , summary = summary
     , n_summaries = n_summaries
diff --git a/inst/include/colourvalues/api/api.hpp b/inst/include/colourvalues/api/api.hpp
index 26811e2..a3c5c2a 100644
--- a/inst/include/colourvalues/api/api.hpp
+++ b/inst/include/colourvalues/api/api.hpp
@@ -1,6 +1,8 @@
 #ifndef R_COLOURVALUES_API_H
 #define R_COLOURVALUES_API_H
 
+#include <Rcpp.h>
+
 #include "colourvalues/api/api_hex.hpp"
 #include "colourvalues/api/api_rgb.hpp"
 
diff --git a/inst/include/colourvalues/api/api_hex.hpp b/inst/include/colourvalues/api/api_hex.hpp
index 82c3142..a86957e 100644
--- a/inst/include/colourvalues/api/api_hex.hpp
+++ b/inst/include/colourvalues/api/api_hex.hpp
@@ -13,14 +13,13 @@ namespace api {
   /*
    * list with matrix palette
    */
-  SEXP colour_values_hex(
+  inline SEXP colour_values_hex(
       Rcpp::List lst,
       Rcpp::NumericMatrix& palette,
       Rcpp::NumericVector& alpha,
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false,
       int n_summaries = 0
@@ -30,7 +29,12 @@ namespace api {
 
     int position = 0;
 
-    Rcpp::List lst_sizes = colourvalues::list::list_size( lst, total_size, existing_type );
+
+    // TODO: get format_type depending on the type of list elements
+    std::string format_type = "numeric";
+    // follow heirarchy of classes:
+    //
+    Rcpp::List lst_sizes = colourvalues::list::list_size( lst, total_size, existing_type, format_type );
 
     switch( existing_type ) {
     case INTSXP: { } // 13
@@ -45,7 +49,7 @@ namespace api {
       }
 
       SEXP coloured_values = colourvalues::colours_hex::colour_value_hex(
-        colours, palette, na_colour, include_alpha, n_summaries, format, format_type, digits
+        colours, palette, na_colour, include_alpha, format_type, n_summaries, format, digits
       );
 
       position = 0;
@@ -89,14 +93,13 @@ namespace api {
   /*
    * list with string palette
    */
-  SEXP colour_values_hex(
+  inline SEXP colour_values_hex(
       Rcpp::List lst,
       std::string& palette,
       Rcpp::NumericVector& alpha,
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false,
       int n_summaries = 0
@@ -106,7 +109,12 @@ namespace api {
 
     int position = 0;
 
-    Rcpp::List lst_sizes = colourvalues::list::list_size( lst, total_size, existing_type );
+
+    // TODO: get format_type depending on the type of list elements
+    std::string format_type = "numeric";
+
+    Rcpp::List lst_sizes = colourvalues::list::list_size( lst, total_size, existing_type, format_type );
+
     switch( existing_type ) {
     case INTSXP: { } // 13
     case REALSXP: { // 14
@@ -120,7 +128,7 @@ namespace api {
       }
 
       SEXP coloured_values = colourvalues::colours_hex::colour_value_hex(
-        colours, palette, na_colour, alpha, include_alpha, n_summaries, format, format_type, digits
+        colours, palette, na_colour, alpha, include_alpha, format_type, n_summaries, format, digits
       );
 
       position = 0;
@@ -141,9 +149,9 @@ namespace api {
     default: {
 
       if( n_summaries > 0 ) {
-        Rcpp::warning("n_summaries not valid for character values, using summary = T");
-        summary = true;
-      }
+      Rcpp::warning("n_summaries not valid for character values, using summary = T");
+      summary = true;
+    }
 
       Rcpp::StringVector colours( total_size );
       colourvalues::list::unlist_list( lst, lst_sizes, colours, position );
@@ -175,37 +183,37 @@ namespace api {
    * when palette is unknown, but vector is numeric
    */
   inline SEXP colour_values_hex(
-    Rcpp::NumericVector& x,
-    SEXP palette,
-    Rcpp::NumericVector& alpha,
-    std::string& na_colour,
-    bool include_alpha = true,
-    bool format = false,
-    std::string format_type = "numeric",
-    int digits = 2,
-    int n_summaries = 0
+      Rcpp::NumericVector& x,
+      SEXP palette,
+      Rcpp::NumericVector& alpha,
+      std::string& format_type,
+      std::string& na_colour,
+      bool include_alpha = true,
+      bool format = false,
+      int digits = 2,
+      int n_summaries = 0
   ) {
 
     //Rcpp::Rcout << "NumericVector x, SEXP palette " << std::endl;
 
     switch( TYPEOF( palette ) ) {
-      // STringVector - needs to get std::string
+    // STringVector - needs to get std::string
     case STRSXP: {
       Rcpp::StringVector sv = Rcpp::as< Rcpp::StringVector >( palette );
       Rcpp::String s = sv[0];
       std::string pal = s;
       return colourvalues::colours_hex::colour_value_hex(
-        x, pal, na_colour, alpha, include_alpha, n_summaries, format, format_type, digits
+        x, pal, na_colour, alpha, include_alpha, format_type, n_summaries, format, digits
       );
     }
     case INTSXP: {}
     case REALSXP: {
       if( !Rf_isMatrix( palette ) ) {
-        Rcpp::stop("Unknown palette type - expecting a matrix");
-      }
+      Rcpp::stop("Unknown palette type - expecting a matrix");
+    }
       Rcpp::NumericMatrix pal = Rcpp::as< Rcpp::NumericMatrix >( palette );
       return colourvalues::colours_hex::colour_value_hex(
-        x, pal, na_colour, include_alpha, n_summaries, format, format_type, digits
+        x, pal, na_colour, include_alpha, format_type, n_summaries, format, digits
       );
     }
     default: {
@@ -222,10 +230,10 @@ namespace api {
       Rcpp::StringVector& x,
       SEXP palette,
       Rcpp::NumericVector& alpha,
+      std::string& format_type,
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false
   ) {
@@ -267,25 +275,25 @@ namespace api {
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false,
       int n_summaries = 0
   ) {
     //Rcpp::Rcout << "SEXP x, NumericMatrix palette " << std::endl;
     //Rcpp::Rcout << "include_alpha: " << include_alpha << std::endl;
+    std::string format_type = colourvalues::format::get_format_type( x );
 
     switch( TYPEOF( x ) ) {
     case INTSXP: {}
     case REALSXP: {
       Rcpp::NumericVector nv = Rcpp::as< Rcpp::NumericVector >( x );
       return colourvalues::colours_hex::colour_value_hex(
-        nv, palette, na_colour, include_alpha, n_summaries, format, format_type, digits
+        nv, palette, na_colour, include_alpha, format_type, n_summaries, format, digits
       );
     }
     case VECSXP: { // list
       Rcpp::List lst = Rcpp::as< Rcpp::List >( x );
-      return colour_values_hex( lst, palette, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries );
+      return colour_values_hex( lst, palette, alpha, na_colour, include_alpha, format, digits, summary, n_summaries );
 
     }
     case LGLSXP: {} // as.character
@@ -309,7 +317,6 @@ namespace api {
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false,
       int n_summaries = 0
@@ -317,6 +324,7 @@ namespace api {
 
     //Rcpp::Rcout << "SEXP x, StringVector palette " << std::endl;
     //Rcpp::Rcout << "typeof x: " << TYPEOF( x ) << std::endl;
+    std::string format_type = colourvalues::format::get_format_type( x );
 
     Rcpp::String p = palette[0];
     std::string pal = p;
@@ -331,7 +339,7 @@ namespace api {
     } else {
       Rcpp::NumericVector nv = Rcpp::clone(x);
       return colourvalues::colours_hex::colour_value_hex(
-        nv, pal, na_colour, alpha, include_alpha, n_summaries, format, format_type, digits
+        nv, pal, na_colour, alpha, include_alpha, format_type, n_summaries, format, digits
       );
     }
     }
@@ -339,12 +347,12 @@ namespace api {
       //Rcpp::NumericVector nv = Rcpp::as< Rcpp::NumericVector >( x );
       Rcpp::NumericVector nv = Rcpp::clone(x);
       return colourvalues::colours_hex::colour_value_hex(
-        nv, pal, na_colour, alpha, include_alpha, n_summaries, format, format_type, digits
+        nv, pal, na_colour, alpha, include_alpha, format_type, n_summaries, format, digits
       );
     }
     case VECSXP: { // list
       Rcpp::List lst = Rcpp::as< Rcpp::List >( x );
-      return colour_values_hex( lst, pal, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries );
+      return colour_values_hex( lst, pal, alpha, na_colour, include_alpha, format, digits, summary, n_summaries );
     }
     case LGLSXP: {} // as.character
     default: {
@@ -369,27 +377,28 @@ namespace api {
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false,
       int n_summaries = 0
   ) {
 
     //Rcpp::Rcout << "SEXP x, SEXP palette " << std::endl;
+    std::string format_type = colourvalues::format::get_format_type( x );
+    //Rcpp::Rcout << "format_type: " << format_type << std::endl;
 
     switch( TYPEOF( palette ) ) {
     case INTSXP: {}
     case REALSXP: {
       Rcpp::NumericMatrix pal = Rcpp::as< Rcpp::NumericMatrix >( palette );
       return colour_values_hex(
-        x, pal, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries
+        x, pal, alpha, na_colour, include_alpha, format, digits, summary, n_summaries
       );
       break;
     }
     case STRSXP: {
       Rcpp::StringVector sv = Rcpp::as< Rcpp::StringVector >( palette );
       return colour_values_hex(
-        x, sv, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries
+        x, sv, alpha, na_colour, include_alpha, format, digits, summary, n_summaries
       );
       break;
     }
@@ -403,7 +412,6 @@ namespace api {
 
   }
 
-
 } // api
 } // colourvalues
 
diff --git a/inst/include/colourvalues/api/api_rgb.hpp b/inst/include/colourvalues/api/api_rgb.hpp
index 52329d1..411bb27 100644
--- a/inst/include/colourvalues/api/api_rgb.hpp
+++ b/inst/include/colourvalues/api/api_rgb.hpp
@@ -13,14 +13,13 @@ namespace api {
   /*
    * list with string palette
    */
-  SEXP colour_values_rgb(
+  inline SEXP colour_values_rgb(
       Rcpp::List lst,
       Rcpp::NumericMatrix& palette,
       Rcpp::NumericVector& alpha,
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false,
       int n_summaries = 0
@@ -30,7 +29,12 @@ namespace api {
 
     int position = 0;
 
-    Rcpp::List lst_sizes = colourvalues::list::list_size( lst, total_size, existing_type );
+
+    // TODO: get format_type depending on the type of list elements
+    std::string format_type = "character";
+
+    Rcpp::List lst_sizes = colourvalues::list::list_size( lst, total_size, existing_type, format_type );
+
     switch( existing_type ) {
     case INTSXP: { } // 13
     case REALSXP: { // 14
@@ -45,7 +49,7 @@ namespace api {
       }
 
       SEXP coloured_values = colourvalues::colours_rgb::colour_value_rgb(
-        colours, palette, na_colour, include_alpha, n_summaries, format, format_type, digits
+        colours, palette, na_colour, include_alpha, format_type, n_summaries, format, digits
       );
 
       position = 0;
@@ -100,14 +104,13 @@ namespace api {
   /*
    * list with string palette
    */
-  SEXP colour_values_rgb(
+  inline SEXP colour_values_rgb(
       Rcpp::List lst,
       std::string& palette,
       Rcpp::NumericVector& alpha,
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false,
       int n_summaries = 0
@@ -119,7 +122,12 @@ namespace api {
 
     //Rcpp::Rcout << "now doing list " << std::endl;
 
-    Rcpp::List lst_sizes = colourvalues::list::list_size( lst, total_size, existing_type );
+
+    // TODO: get format_type depending on the type of list elements
+    std::string format_type = "character";
+
+    Rcpp::List lst_sizes = colourvalues::list::list_size( lst, total_size, existing_type, format_type );
+
     switch( existing_type ) {
     case INTSXP: { } // 13
     case REALSXP: { // 14
@@ -135,7 +143,7 @@ namespace api {
 
       //Rcpp::Rcout << "colouring values" << std::endl;
       SEXP coloured_values = colourvalues::colours_rgb::colour_value_rgb(
-        colours, palette, na_colour, alpha, include_alpha, n_summaries, format, format_type, digits
+        colours, palette, na_colour, alpha, include_alpha, format_type, n_summaries, format, digits
       );
       //Rcpp::Rcout << "coloured values" << std::endl;
 
@@ -157,9 +165,9 @@ namespace api {
     default: {
 
       if( n_summaries > 0 ) {
-        Rcpp::warning("n_summaries not valid for character values, using summary = T");
-        summary = true;
-      }
+      Rcpp::warning("n_summaries not valid for character values, using summary = T");
+      summary = true;
+    }
 
       Rcpp::StringVector colours( total_size );
       colourvalues::list::unlist_list( lst, lst_sizes, colours, position );
@@ -194,10 +202,10 @@ namespace api {
       Rcpp::NumericVector& x,
       SEXP palette,
       Rcpp::NumericVector& alpha,
+      std::string& format_type,
       std::string& na_colour,
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       int n_summaries = 0
   ) {
@@ -211,7 +219,7 @@ namespace api {
       Rcpp::String s = sv[0];
       std::string pal = s;
       return colourvalues::colours_rgb::colour_value_rgb(
-        x, pal, na_colour, alpha, include_alpha, n_summaries, format, format_type, digits
+        x, pal, na_colour, alpha, include_alpha, format_type, n_summaries, format, digits
       );
     }
     case INTSXP: {}
@@ -221,7 +229,7 @@ namespace api {
     }
       Rcpp::NumericMatrix pal = Rcpp::as< Rcpp::NumericMatrix >( palette );
       return colourvalues::colours_rgb::colour_value_rgb(
-        x, pal, na_colour, include_alpha, n_summaries, format, format_type, digits
+        x, pal, na_colour, include_alpha, format_type, n_summaries, format, digits
       );
     }
     default: {
@@ -238,10 +246,10 @@ namespace api {
       Rcpp::StringVector& x,
       SEXP palette,
       Rcpp::NumericVector& alpha,
+      std::string& format_type,
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false
   ) {
@@ -283,7 +291,6 @@ namespace api {
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false,
       int n_summaries = 0
@@ -291,12 +298,14 @@ namespace api {
     //Rcpp::Rcout << "SEXP x, NumericMatrix palette " << std::endl;
     //Rcpp::Rcout << "include_alpha: " << include_alpha << std::endl;
 
+    std::string format_type = colourvalues::format::get_format_type( x );
+
     switch( TYPEOF( x ) ) {
     case INTSXP: {}
     case REALSXP: {
       Rcpp::NumericVector nv = Rcpp::as< Rcpp::NumericVector >( x );
       return colourvalues::colours_rgb::colour_value_rgb(
-        nv, palette, na_colour, include_alpha, n_summaries, format, format_type, digits
+        nv, palette, na_colour, include_alpha, format_type, n_summaries, format, digits
       );
     }
     case VECSXP: { // list
@@ -326,7 +335,6 @@ namespace api {
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false,
       int n_summaries = 0
@@ -334,6 +342,7 @@ namespace api {
 
     //Rcpp::Rcout << "SEXP x, StringVector palette " << std::endl;
     //Rcpp::Rcout << "typeof x: " << TYPEOF( x ) << std::endl;
+    std::string format_type = colourvalues::format::get_format_type( x );
 
     Rcpp::String p = palette[0];
     std::string pal = p;
@@ -348,7 +357,7 @@ namespace api {
     } else {
       Rcpp::NumericVector nv = Rcpp::clone(x);
       return colourvalues::colours_rgb::colour_value_rgb(
-        nv, pal, na_colour, alpha, include_alpha, n_summaries, format, format_type, digits
+        nv, pal, na_colour, alpha, include_alpha, format_type, n_summaries, format, digits
       );
     }
     }
@@ -356,13 +365,13 @@ namespace api {
       //Rcpp::NumericVector nv = Rcpp::as< Rcpp::NumericVector >( x );
       Rcpp::NumericVector nv = Rcpp::clone(x);
       return colourvalues::colours_rgb::colour_value_rgb(
-        nv, pal, na_colour, alpha, include_alpha, n_summaries, format, format_type, digits
+        nv, pal, na_colour, alpha, include_alpha, format_type, n_summaries, format, digits
       );
     }
     case VECSXP: { // list
       Rcpp::List lst = Rcpp::as< Rcpp::List >( x );
       //Rcpp::Rcout << "starting list " << std::endl;
-      return colour_values_rgb( lst, pal, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries );
+      return colour_values_rgb( lst, pal, alpha, na_colour, include_alpha, format, digits, summary, n_summaries );
 
     }
     case LGLSXP: {} // as.character
@@ -388,7 +397,6 @@ namespace api {
       std::string na_colour = "#808080",
       bool include_alpha = true,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2,
       bool summary = false,
       int n_summaries = 0
@@ -401,14 +409,14 @@ namespace api {
     case REALSXP: {
       Rcpp::NumericMatrix pal = Rcpp::as< Rcpp::NumericMatrix >( palette );
       return colour_values_rgb(
-        x, pal, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries
+        x, pal, alpha, na_colour, include_alpha, format, digits, summary, n_summaries
       );
       break;
     }
     case STRSXP: {
       Rcpp::StringVector sv = Rcpp::as< Rcpp::StringVector >( palette );
       return colour_values_rgb(
-        x, sv, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries
+        x, sv, alpha, na_colour, include_alpha, format, digits, summary, n_summaries
       );
       break;
     }
diff --git a/inst/include/colourvalues/colours/colours_hex.hpp b/inst/include/colourvalues/colours/colours_hex.hpp
index 2e1fe3a..7814dc5 100644
--- a/inst/include/colourvalues/colours/colours_hex.hpp
+++ b/inst/include/colourvalues/colours/colours_hex.hpp
@@ -25,9 +25,6 @@ namespace colours_hex {
       bool& include_alpha
    ) {
 
-    //Rcpp::Rcout << "colour_values_to_hex " << std::endl;
-    //Rcpp::Rcout << "include_alpha: " << include_alpha << std::endl;
-
     int n = x.size();
     double colours = red.size();
 
@@ -80,14 +77,41 @@ namespace colours_hex {
     return hex_strings;
   }
 
+  // combining:
+  // - 'format'
+
+  inline Rcpp::List create_summary_output(
+      Rcpp::StringVector& full_hex,
+      Rcpp::StringVector& summary_values,
+      Rcpp::StringVector& summary_hex
+  ) {
+    return Rcpp::List::create(
+      _["colours"] = full_hex,
+      _["summary_values"] = summary_values,
+      _["summary_colours"] = summary_hex
+    );
+  }
+
+  inline Rcpp::List create_summary_output(
+      Rcpp::StringVector& full_hex,
+      SEXP& summary_values,
+      Rcpp::StringVector& summary_hex
+   ) {
+    return Rcpp::List::create(
+      _["colours"] = full_hex,
+      _["summary_values"] = summary_values,
+      _["summary_colours"] = summary_hex
+    );
+  }
+
   inline SEXP colour_value_hex(
     Rcpp::NumericVector& x,
     Rcpp::NumericMatrix& palette,
     std::string& na_colour,
     bool include_alpha,
+    std::string& format_type,
     int n_summaries = 0,
     bool format = false,
-    std::string format_type = "numeric",
     int digits = 2
   ) {
 
@@ -120,11 +144,8 @@ namespace colours_hex {
 
       Rcpp::StringVector summary_hex = colour_values_to_hex( summary, red, green, blue, alpha_summary, alpha_type, na_colour, include_alpha ); // uses full opacity
       Rcpp::StringVector full_hex = colour_values_to_hex( x, red, green, blue, alpha_full, alpha_type, na_colour, include_alpha );
-      return Rcpp::List::create(
-        _["colours"] = full_hex,
-        _["summary_values"] = summary_values,
-        _["summary_colours"] = summary_hex
-      );
+
+      return create_summary_output(full_hex, summary_values, summary_hex );
     }
 
     return colour_values_to_hex( x, red, green, blue, alpha_full, alpha_type, na_colour, include_alpha );
@@ -136,10 +157,11 @@ namespace colours_hex {
       std::string& na_colour,
       Rcpp::NumericVector& alpha,
       bool include_alpha,
+      std::string& format_type,
       int n_summaries = 0,
       bool format = false,
-      std::string format_type = "numeric",
-      int digits = 2) {
+      int digits = 2
+   ) {
 
     int x_size = x.size();
     int alpha_type = colourvalues::alpha::make_alpha_type( alpha.size(), x_size, 0 );
@@ -168,11 +190,7 @@ namespace colours_hex {
       Rcpp::StringVector summary_hex = colour_values_to_hex(summary, red, green, blue, alpha_summary, alpha_type, na_colour, include_alpha);
       Rcpp::StringVector full_hex = colour_values_to_hex(x, red, green, blue, alpha_full, alpha_type, na_colour, include_alpha);
 
-      return Rcpp::List::create(
-        _["colours"] = full_hex,
-        _["summary_values"] = summary_values,
-        _["summary_colours"] = summary_hex
-        );
+      return create_summary_output(full_hex, summary_values, summary_hex );
     }
     return colour_values_to_hex(x, red, green, blue, alpha_full, alpha_type, na_colour, include_alpha);
   }
@@ -184,9 +202,6 @@ namespace colours_hex {
       bool include_alpha,
       bool summary = false) {
 
-    //Rcpp::Rcout << "colour_value_hex" << std::endl;
-    //Rcpp::Rcout << "include_alpha: " << include_alpha << std::endl;
-
     colourvalues::utils::matrix_palette_check( palette );
     int alpha_type = colourvalues::alpha::make_alpha_type( 0, x.size(), palette.ncol() );
 
@@ -210,11 +225,8 @@ namespace colours_hex {
 
       Rcpp::StringVector summary_hex = colour_values_to_hex( nv, red, green, blue, alpha_summary, alpha_type, na_colour, include_alpha );
       Rcpp::StringVector full_hex = colour_values_to_hex( out_nv, red, green, blue, alpha, alpha_type, na_colour, include_alpha );
-      return Rcpp::List::create(
-        _["colours"] = full_hex,
-        _["summary_values"] = lvls,
-        _["summary_colours"] = summary_hex
-      );
+
+      return create_summary_output(full_hex, lvls, summary_hex );
     }
     //Rcpp::Rcout << "about to do the conversion - include_alpha: " << include_alpha << std::endl;
     return colour_values_to_hex( out_nv, red, green, blue, alpha, alpha_type, na_colour, include_alpha );
@@ -228,8 +240,6 @@ namespace colours_hex {
       bool include_alpha,
       bool summary = false) {
 
-    //Rcpp::Rcout << "inside colours_hex::colour_value_hex" << std::endl;
-
     int x_size = x.size();
     int alpha_type = colourvalues::alpha::make_alpha_type( alpha.size(), x_size, 0 );
 
@@ -246,9 +256,7 @@ namespace colours_hex {
     Rcpp::NumericVector out_nv = colourvalues::utils::resolve_string_vector( x, lvls );
 
     if ( summary ) {
-      //Rcpp::Rcout << "making summary " << std::endl;
       Rcpp::IntegerVector summary_values = Rcpp::seq_len( lvls.length() );
-      //Rcpp::Rcout << "summary values " << summary_values << std::endl;
       Rcpp::NumericVector nv = Rcpp::as< Rcpp::NumericVector >( summary_values );
 
       int x_size = x.size();
@@ -256,15 +264,9 @@ namespace colours_hex {
       Rcpp::NumericVector alpha_summary( n_alpha_summary, 255.0 );
 
       Rcpp::StringVector summary_hex = colour_values_to_hex( nv, red, green, blue, alpha_summary, alpha_type, na_colour, include_alpha );
-      //Rcpp::Rcout << "summary_hex " << summary_hex << std::endl;
       Rcpp::StringVector full_hex = colour_values_to_hex( out_nv, red, green, blue, alpha_full, alpha_type, na_colour, include_alpha );
-      //Rcpp::Rcout << "full_hex: " << full_hex << std::endl;
 
-      return Rcpp::List::create(
-        _["colours"] = full_hex,
-        _["summary_values"] = lvls,
-        _["summary_colours"] = summary_hex
-      );
+      return create_summary_output(full_hex, lvls, summary_hex );
     }
 
     return colour_values_to_hex( out_nv, red, green, blue, alpha_full, alpha_type, na_colour, include_alpha );
diff --git a/inst/include/colourvalues/colours/colours_rgb.hpp b/inst/include/colourvalues/colours/colours_rgb.hpp
index 292d0f1..d3145f3 100644
--- a/inst/include/colourvalues/colours/colours_rgb.hpp
+++ b/inst/include/colourvalues/colours/colours_rgb.hpp
@@ -86,9 +86,9 @@ namespace colours_rgb {
       Rcpp::NumericMatrix& palette,
       std::string& na_colour,
       bool include_alpha,
+      std::string& format_type,
       int n_summaries = 0,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2
   ) {
 
@@ -137,9 +137,9 @@ namespace colours_rgb {
       std::string& na_colour,
       Rcpp::NumericVector& alpha,
       bool include_alpha,
+      std::string& format_type,
       int n_summaries = 0,
       bool format = false,
-      std::string format_type = "numeric",
       int digits = 2) {
 
     int x_size = x.size();
diff --git a/inst/include/colourvalues/format/format.hpp b/inst/include/colourvalues/format/format.hpp
index ca030ef..b8d828d 100644
--- a/inst/include/colourvalues/format/format.hpp
+++ b/inst/include/colourvalues/format/format.hpp
@@ -4,6 +4,9 @@
 #include <Rcpp.h>
 #include <iostream>
 #include <boost/date_time.hpp>
+
+#include "colourvalues/utils/utils.hpp"
+
 // #include <boost/lexical_cast.hpp>
 
 // [[Rcpp::depends(BH)]]
@@ -11,6 +14,34 @@
 namespace colourvalues {
 namespace format {
 
+  /*
+   * Determins the type of formatting requried for summary values (legend)
+   *
+   */
+  inline std::string get_format_type( SEXP x ) {
+
+    std::string format_type;
+
+    Rcpp::CharacterVector cls = colourvalues::utils::getRClass( x );
+
+    //Rcpp::Rcout << "cls: " << cls << std::endl;
+
+    if( colourvalues::utils::is_in( "Date", cls ) ) {
+      format_type = "Date";
+    } else if ( colourvalues::utils::is_in("POSIXct", cls) ) {
+      format_type = "POSIXct";
+    } else if ( colourvalues::utils::is_in("POSIXlt", cls) ) {
+      format_type = "POSIXct";
+    } else if ( colourvalues::utils::is_in("logical", cls) ) {
+      format_type = "character";
+    } else if ( colourvalues::utils::is_in("character", cls) ) {
+      format_type = "character";
+    } else {
+      format_type = "numeric";
+    }
+    return format_type;
+  }
+
   inline Rcpp::StringVector date_to_string( SEXP v, int n ) {
 
     int i;
@@ -19,7 +50,7 @@ namespace format {
 
     for ( i = 0; i < n; i++ ) {
       Rcpp::Date d = nv[i];
-      boost::gregorian::date gd = boost::gregorian::date(d.getYear(), d.getMonth(), d.getDay());
+      boost::gregorian::date gd = boost::gregorian::date( d.getYear(), d.getMonth(), d.getDay() );
       std::string s = boost::gregorian::to_iso_extended_string( gd );
       sv[i] = s.c_str();
     }
@@ -61,7 +92,10 @@ namespace format {
     return sv;
   }
 
-  inline SEXP format_summary( SEXP summary_values, std::string format_type, int n_summaries, int digits ) {
+  inline SEXP format_summary( SEXP summary_values, std::string& format_type, int n_summaries, int digits ) {
+
+    //std::string format_type = get_format_type( summary_values );
+
     if (format_type == "numeric" ) {
       return colourvalues::format::numeric_to_string( summary_values, n_summaries, digits);
     // } else if ( format_type == "integer" ) {
diff --git a/inst/include/colourvalues/list/list.hpp b/inst/include/colourvalues/list/list.hpp
index 8975c3e..3119ee9 100644
--- a/inst/include/colourvalues/list/list.hpp
+++ b/inst/include/colourvalues/list/list.hpp
@@ -3,6 +3,7 @@
 #define R_COLOURVALUES_LIST
 
 #include <Rcpp.h>
+#include "colourvalues/format/format.hpp"
 //#include "colourvalues/colours/colours_hex.hpp"
 
 /*colouring a list
@@ -57,19 +58,24 @@ namespace list {
       return 16;
    }
 
-   inline Rcpp::List list_size( const Rcpp::List& lst, int& total_size, int& existing_type ) {
+   inline Rcpp::List list_size( const Rcpp::List& lst, int& total_size, int& existing_type, std::string& existing_format ) {
       std::size_t n = lst.size();
       Rcpp::List res( n ); // create a list to store the size corresponding to each list element
       std::size_t i;
       for( i = 0; i < n; i++ ) {
          switch( TYPEOF( lst[i] ) ) {
          case VECSXP: {
-            res[ i ] = list_size( lst[i], total_size, existing_type );
+            res[ i ] = list_size( lst[i], total_size, existing_type, existing_format );
             break;
          }
          default: {
             int n_elements = Rf_length( lst[i] );
             int new_type = TYPEOF( lst[i] );
+            std::string new_format = colourvalues::format::get_format_type( lst[i] );
+            //Rcpp::Rcout << "format_type : " << format_type << std::endl;
+            if( new_format != existing_format ) {
+               existing_format = "character";
+            }
             existing_type = vector_type( new_type, existing_type );
             res[i] = n_elements;
             total_size += n_elements;
@@ -161,7 +167,7 @@ namespace list {
    /*
     * @param lst - the original input list
     * @param lst_sizes - the dimensions of the list
-    * @param colorus - vector of values which will go into colour_values_hex()
+    * @param colours - vector of values which will go into colour_values_hex()
     */
    inline void unlist_list(
          const Rcpp::List& lst, const Rcpp::List& lst_sizes,
diff --git a/inst/include/colourvalues/utils/utils.hpp b/inst/include/colourvalues/utils/utils.hpp
index f4efbf0..dbadd79 100644
--- a/inst/include/colourvalues/utils/utils.hpp
+++ b/inst/include/colourvalues/utils/utils.hpp
@@ -6,6 +6,47 @@
 namespace colourvalues {
 namespace utils {
 
+  inline bool is_in( const char* x, Rcpp::CharacterVector v ) {
+    int n = v.size();
+    int i;
+    for( i = 0; i < n; i++ ) {
+      if( v[i] == x ) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  template < int RTYPE >
+  inline Rcpp::CharacterVector rClass( Rcpp::Vector< RTYPE > v ) {
+    if( Rf_isNull( v.attr("class")) ) {
+      return "";
+    }
+    return v.attr("class");
+  }
+
+  inline Rcpp::CharacterVector getRClass( SEXP obj ) {
+
+    switch( TYPEOF( obj ) ) {
+    case REALSXP:
+      return rClass< REALSXP >( obj );
+      //return "numeric";
+    case VECSXP:
+      return rClass< VECSXP >( obj );
+      //return "character";
+    case INTSXP:
+      return rClass< INTSXP >( obj );
+      //return "numeric";
+    case LGLSXP:
+      //return rClass< LGLSXP >( obj );
+      return "logical";
+    case STRSXP:
+      //return rClass< STRSXP >( obj );
+      return "character";
+    }
+    return "";
+  }
+
   inline void matrix_palette_check( Rcpp::NumericMatrix& pal ) {
     if( pal.nrow() < 5 ) {
       Rcpp::stop("Matrix palettes must have at least 5 rows");
diff --git a/src/ColourValues.cpp b/src/ColourValues.cpp
index c2ab4a5..7429e42 100644
--- a/src/ColourValues.cpp
+++ b/src/ColourValues.cpp
@@ -1,8 +1,6 @@
 #include <Rcpp.h>
 
-#include "colourvalues/api/api_hex.hpp"
-#include "colourvalues/api/api_rgb.hpp"
-
+#include "colourvalues/api/api.hpp"
 
 // [[Rcpp::export]]
 SEXP rcpp_colour_values_hex(
@@ -12,7 +10,6 @@ SEXP rcpp_colour_values_hex(
     std::string na_colour = "#808080",
     bool include_alpha = true,
     bool format = false,
-    std::string format_type = "numeric",
     int digits = 2,
     bool summary = false,
     int n_summaries = 0
@@ -23,7 +20,7 @@ SEXP rcpp_colour_values_hex(
   //Rcpp::Rcout << "summary " << summary << std::endl;
 
   return colourvalues::api::colour_values_hex(
-    x, palette, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries
+    x, palette, alpha, na_colour, include_alpha, format, digits, summary, n_summaries
   );
 }
 
@@ -36,14 +33,13 @@ SEXP rcpp_colour_values_rgb(
     std::string na_colour = "#808080",
     bool include_alpha = true,
     bool format = false,
-    std::string format_type = "numeric",
     int digits = 2,
     bool summary = false,
     int n_summaries = 0
 ) {
 
   return colourvalues::api::colour_values_rgb(
-    x, palette, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries
+    x, palette, alpha, na_colour, include_alpha, format, digits, summary, n_summaries
   );
 }
 
diff --git a/src/RcppExports.cpp b/src/RcppExports.cpp
index 2b9d8b6..217c965 100644
--- a/src/RcppExports.cpp
+++ b/src/RcppExports.cpp
@@ -6,8 +6,8 @@
 using namespace Rcpp;
 
 // rcpp_colour_values_hex
-SEXP rcpp_colour_values_hex(SEXP x, SEXP palette, Rcpp::NumericVector& alpha, std::string na_colour, bool include_alpha, bool format, std::string format_type, int digits, bool summary, int n_summaries);
-RcppExport SEXP _colourvalues_rcpp_colour_values_hex(SEXP xSEXP, SEXP paletteSEXP, SEXP alphaSEXP, SEXP na_colourSEXP, SEXP include_alphaSEXP, SEXP formatSEXP, SEXP format_typeSEXP, SEXP digitsSEXP, SEXP summarySEXP, SEXP n_summariesSEXP) {
+SEXP rcpp_colour_values_hex(SEXP x, SEXP palette, Rcpp::NumericVector& alpha, std::string na_colour, bool include_alpha, bool format, int digits, bool summary, int n_summaries);
+RcppExport SEXP _colourvalues_rcpp_colour_values_hex(SEXP xSEXP, SEXP paletteSEXP, SEXP alphaSEXP, SEXP na_colourSEXP, SEXP include_alphaSEXP, SEXP formatSEXP, SEXP digitsSEXP, SEXP summarySEXP, SEXP n_summariesSEXP) {
 BEGIN_RCPP
     Rcpp::RObject rcpp_result_gen;
     Rcpp::RNGScope rcpp_rngScope_gen;
@@ -17,17 +17,16 @@ BEGIN_RCPP
     Rcpp::traits::input_parameter< std::string >::type na_colour(na_colourSEXP);
     Rcpp::traits::input_parameter< bool >::type include_alpha(include_alphaSEXP);
     Rcpp::traits::input_parameter< bool >::type format(formatSEXP);
-    Rcpp::traits::input_parameter< std::string >::type format_type(format_typeSEXP);
     Rcpp::traits::input_parameter< int >::type digits(digitsSEXP);
     Rcpp::traits::input_parameter< bool >::type summary(summarySEXP);
     Rcpp::traits::input_parameter< int >::type n_summaries(n_summariesSEXP);
-    rcpp_result_gen = Rcpp::wrap(rcpp_colour_values_hex(x, palette, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries));
+    rcpp_result_gen = Rcpp::wrap(rcpp_colour_values_hex(x, palette, alpha, na_colour, include_alpha, format, digits, summary, n_summaries));
     return rcpp_result_gen;
 END_RCPP
 }
 // rcpp_colour_values_rgb
-SEXP rcpp_colour_values_rgb(SEXP x, SEXP palette, Rcpp::NumericVector& alpha, std::string na_colour, bool include_alpha, bool format, std::string format_type, int digits, bool summary, int n_summaries);
-RcppExport SEXP _colourvalues_rcpp_colour_values_rgb(SEXP xSEXP, SEXP paletteSEXP, SEXP alphaSEXP, SEXP na_colourSEXP, SEXP include_alphaSEXP, SEXP formatSEXP, SEXP format_typeSEXP, SEXP digitsSEXP, SEXP summarySEXP, SEXP n_summariesSEXP) {
+SEXP rcpp_colour_values_rgb(SEXP x, SEXP palette, Rcpp::NumericVector& alpha, std::string na_colour, bool include_alpha, bool format, int digits, bool summary, int n_summaries);
+RcppExport SEXP _colourvalues_rcpp_colour_values_rgb(SEXP xSEXP, SEXP paletteSEXP, SEXP alphaSEXP, SEXP na_colourSEXP, SEXP include_alphaSEXP, SEXP formatSEXP, SEXP digitsSEXP, SEXP summarySEXP, SEXP n_summariesSEXP) {
 BEGIN_RCPP
     Rcpp::RObject rcpp_result_gen;
     Rcpp::RNGScope rcpp_rngScope_gen;
@@ -37,11 +36,10 @@ BEGIN_RCPP
     Rcpp::traits::input_parameter< std::string >::type na_colour(na_colourSEXP);
     Rcpp::traits::input_parameter< bool >::type include_alpha(include_alphaSEXP);
     Rcpp::traits::input_parameter< bool >::type format(formatSEXP);
-    Rcpp::traits::input_parameter< std::string >::type format_type(format_typeSEXP);
     Rcpp::traits::input_parameter< int >::type digits(digitsSEXP);
     Rcpp::traits::input_parameter< bool >::type summary(summarySEXP);
     Rcpp::traits::input_parameter< int >::type n_summaries(n_summariesSEXP);
-    rcpp_result_gen = Rcpp::wrap(rcpp_colour_values_rgb(x, palette, alpha, na_colour, include_alpha, format, format_type, digits, summary, n_summaries));
+    rcpp_result_gen = Rcpp::wrap(rcpp_colour_values_rgb(x, palette, alpha, na_colour, include_alpha, format, digits, summary, n_summaries));
     return rcpp_result_gen;
 END_RCPP
 }
@@ -78,6 +76,28 @@ BEGIN_RCPP
     return rcpp_result_gen;
 END_RCPP
 }
+// rcpp_get_format_type
+std::string rcpp_get_format_type(SEXP palette_type);
+RcppExport SEXP _colourvalues_rcpp_get_format_type(SEXP palette_typeSEXP) {
+BEGIN_RCPP
+    Rcpp::RObject rcpp_result_gen;
+    Rcpp::RNGScope rcpp_rngScope_gen;
+    Rcpp::traits::input_parameter< SEXP >::type palette_type(palette_typeSEXP);
+    rcpp_result_gen = Rcpp::wrap(rcpp_get_format_type(palette_type));
+    return rcpp_result_gen;
+END_RCPP
+}
+// rcpp_get_r_class
+Rcpp::CharacterVector rcpp_get_r_class(SEXP obj);
+RcppExport SEXP _colourvalues_rcpp_get_r_class(SEXP objSEXP) {
+BEGIN_RCPP
+    Rcpp::RObject rcpp_result_gen;
+    Rcpp::RNGScope rcpp_rngScope_gen;
+    Rcpp::traits::input_parameter< SEXP >::type obj(objSEXP);
+    rcpp_result_gen = Rcpp::wrap(rcpp_get_r_class(obj));
+    return rcpp_result_gen;
+END_RCPP
+}
 // rcpp_vector_type
 int rcpp_vector_type(int new_type, int existing_type);
 RcppExport SEXP _colourvalues_rcpp_vector_type(SEXP new_typeSEXP, SEXP existing_typeSEXP) {
@@ -91,15 +111,16 @@ BEGIN_RCPP
 END_RCPP
 }
 // rcpp_list_size
-Rcpp::List rcpp_list_size(const Rcpp::List& lst, int& total_size, int& existing_type);
-RcppExport SEXP _colourvalues_rcpp_list_size(SEXP lstSEXP, SEXP total_sizeSEXP, SEXP existing_typeSEXP) {
+Rcpp::List rcpp_list_size(const Rcpp::List& lst, int& total_size, int& existing_type, std::string& format_type);
+RcppExport SEXP _colourvalues_rcpp_list_size(SEXP lstSEXP, SEXP total_sizeSEXP, SEXP existing_typeSEXP, SEXP format_typeSEXP) {
 BEGIN_RCPP
     Rcpp::RObject rcpp_result_gen;
     Rcpp::RNGScope rcpp_rngScope_gen;
     Rcpp::traits::input_parameter< const Rcpp::List& >::type lst(lstSEXP);
     Rcpp::traits::input_parameter< int& >::type total_size(total_sizeSEXP);
     Rcpp::traits::input_parameter< int& >::type existing_type(existing_typeSEXP);
-    rcpp_result_gen = Rcpp::wrap(rcpp_list_size(lst, total_size, existing_type));
+    Rcpp::traits::input_parameter< std::string& >::type format_type(format_typeSEXP);
+    rcpp_result_gen = Rcpp::wrap(rcpp_list_size(lst, total_size, existing_type, format_type));
     return rcpp_result_gen;
 END_RCPP
 }
@@ -638,13 +659,15 @@ END_RCPP
 }
 
 static const R_CallMethodDef CallEntries[] = {
-    {"_colourvalues_rcpp_colour_values_hex", (DL_FUNC) &_colourvalues_rcpp_colour_values_hex, 10},
-    {"_colourvalues_rcpp_colour_values_rgb", (DL_FUNC) &_colourvalues_rcpp_colour_values_rgb, 10},
+    {"_colourvalues_rcpp_colour_values_hex", (DL_FUNC) &_colourvalues_rcpp_colour_values_hex, 9},
+    {"_colourvalues_rcpp_colour_values_rgb", (DL_FUNC) &_colourvalues_rcpp_colour_values_rgb, 9},
     {"_colourvalues_rcpp_convert_hex_to_rgb", (DL_FUNC) &_colourvalues_rcpp_convert_hex_to_rgb, 1},
     {"_colourvalues_rcpp_convert_rgb_mat_to_hex", (DL_FUNC) &_colourvalues_rcpp_convert_rgb_mat_to_hex, 1},
     {"_colourvalues_rcpp_convert_rgb_vec_to_hex", (DL_FUNC) &_colourvalues_rcpp_convert_rgb_vec_to_hex, 1},
+    {"_colourvalues_rcpp_get_format_type", (DL_FUNC) &_colourvalues_rcpp_get_format_type, 1},
+    {"_colourvalues_rcpp_get_r_class", (DL_FUNC) &_colourvalues_rcpp_get_r_class, 1},
     {"_colourvalues_rcpp_vector_type", (DL_FUNC) &_colourvalues_rcpp_vector_type, 2},
-    {"_colourvalues_rcpp_list_size", (DL_FUNC) &_colourvalues_rcpp_list_size, 3},
+    {"_colourvalues_rcpp_list_size", (DL_FUNC) &_colourvalues_rcpp_list_size, 4},
     {"_colourvalues_rcpp_refil_list", (DL_FUNC) &_colourvalues_rcpp_refil_list, 3},
     {"_colourvalues_rcpp_viridis", (DL_FUNC) &_colourvalues_rcpp_viridis, 0},
     {"_colourvalues_rcpp_inferno", (DL_FUNC) &_colourvalues_rcpp_inferno, 0},
diff --git a/src/format.cpp b/src/format.cpp
new file mode 100644
index 0000000..52f68f8
--- /dev/null
+++ b/src/format.cpp
@@ -0,0 +1,16 @@
+#include <Rcpp.h>
+using namespace Rcpp;
+
+#include "colourvalues/format/format.hpp"
+#include "colourvalues/utils/utils.hpp"
+
+
+// [[Rcpp::export]]
+std::string rcpp_get_format_type( SEXP palette_type ) {
+  return colourvalues::format::get_format_type( palette_type );
+}
+
+// [[Rcpp::export]]
+Rcpp::CharacterVector rcpp_get_r_class( SEXP obj ) {
+  return colourvalues::utils::getRClass( obj );
+}
diff --git a/src/list.cpp b/src/list.cpp
index 0a4b0d8..f39b4c7 100644
--- a/src/list.cpp
+++ b/src/list.cpp
@@ -14,8 +14,8 @@ int rcpp_vector_type( int new_type, int existing_type ) {
  * Anything outside those numbers is converted to STRSXP
  */
 // [[Rcpp::export]]
-Rcpp::List rcpp_list_size( const Rcpp::List& lst, int& total_size, int& existing_type ) {
-  return colourvalues::list::list_size( lst, total_size, existing_type );
+Rcpp::List rcpp_list_size( const Rcpp::List& lst, int& total_size, int& existing_type, std::string& format_type ) {
+  return colourvalues::list::list_size( lst, total_size, existing_type, format_type );
 }
 
 
diff --git a/tests/testthat/test-colour_values_hex.R b/tests/testthat/test-colour_values_hex.R
index a78100f..32ff29b 100644
--- a/tests/testthat/test-colour_values_hex.R
+++ b/tests/testthat/test-colour_values_hex.R
@@ -169,7 +169,7 @@ test_that("original vectors returned",{
   y <- 1L:10L
   invisible( colour_values(x) )
   expect_true( all(x == y) )
-  invisible( colour_values_rgb(x))
+  invisible( colour_values_rgb(x) )
   expect_true( all(x == y))
 
   set.seed(1)
diff --git a/tests/testthat/test-format.R b/tests/testthat/test-format.R
new file mode 100644
index 0000000..a011496
--- /dev/null
+++ b/tests/testthat/test-format.R
@@ -0,0 +1,20 @@
+context("format")
+
+test_that("correct format_type is determined",{
+
+  expect_equal( colourvalues:::rcpp_get_format_type("abc"), "character")
+  expect_equal( colourvalues:::rcpp_get_format_type(T), "character")
+  expect_equal( colourvalues:::rcpp_get_format_type(factor(1)), "numeric")
+  expect_equal( colourvalues:::rcpp_get_format_type(as.Date("2018-01-01")), "Date")
+  expect_equal( colourvalues:::rcpp_get_format_type(as.POSIXct("2018-01-01")), "POSIXct")
+  expect_equal( colourvalues:::rcpp_get_format_type(as.POSIXlt("2018-01-01")), "POSIXct")
+  expect_equal( colourvalues:::rcpp_get_format_type(123), "numeric")
+
+  ## TODO
+  ## - does it make sense for a list to have a format type, should it only work on vectors?
+  #expect_equal( colourvalues:::rcpp_get_format_type( list("a") ), "character")
+  #colourvalues:::rcpp_get_r_class( list("a") )
+
+
+  })
+
diff --git a/tests/testthat/test-lists.R b/tests/testthat/test-lists.R
index 7866b87..a7fe203 100644
--- a/tests/testthat/test-lists.R
+++ b/tests/testthat/test-lists.R
@@ -134,6 +134,15 @@ test_that("list produces summary",{
   expect_true( all( res$summary_values == c("1.00000","2.25000","3.50000","4.75000","6.00000") ) )
 
   expect_warning( colour_values( list(letters),  n_summaries = 4) )
+
+  ## Mix
+  l <- list( x = 1, y = "a")
+  res <- colour_values( l, summary = T )
+  expect_true( all( res$summary_values == c("1","a") ) )
+
+  l <- list( x = as.Date("2018-01-01"), y = as.POSIXct("2018-01-01", tz = "GMT"))
+  res <- colour_values( l, n_summaries = 3 )
+  expect_true( all( res$summary_values == c("17532","1514764800")))
 })