diff --git a/R/extratrees.R b/R/extratrees.R
new file mode 100644
index 0000000..e439c24
--- /dev/null
+++ b/R/extratrees.R
@@ -0,0 +1,86 @@
+
+
+# 1 - ExtraTreesRegressor
+# -------------------------------------------------------------------
+
+ExtraTreesRegressor <- R6::R6Class(classname = "ExtraTreesRegressor", inherit = learningmachine::BaseRegressor,
+    public = list(name = "ExtraTreesRegressor", type = "regression", model = NULL, X_train = NULL,
+        y_train = NULL, engine = NULL, params = NULL, initialize = function(name = "ExtraTreesRegressor",
+            type = "regression", model = NULL, X_train = NULL, y_train = NULL, engine = NULL,
+            params = NULL) {
+            self$name <- name
+            self$type <- type
+            self$model <- model
+            self$X_train <- X_train
+            self$y_train <- y_train
+            self$engine <- engine
+            self$params <- params
+        }, fit = function(X, y, ...) {
+            if (is_package_available("ranger") == FALSE) install.packages("ranger",
+                repos = c(CRAN = "https://cloud.r-project.org"))
+            self$X_train <- X
+            self$y_train <- y
+            self$params <- list(...)
+            self$set_model(fit_func_extratrees_regression(x = self$X_train, y = self$y_train,
+                ...))
+            self$set_engine(list(fit = function(x, y) fit_func_extratrees_regression(x,
+                y, ...), predict = predict_func_extratrees))
+            return(base::invisible(self))
+        }, predict = function(X, level = NULL, method = c("splitconformal", "jackknifeplus",
+            "kdesplitconformal", "kdejackknifeplus"), ...) {
+            method <- match.arg(method)
+            super$predict(X = X, level = level, method = method)
+        }))
+
+
+# 2 - ExtraTreesClassifier
+# -------------------------------------------------------------------
+
+ExtraTreesClassifier <- R6::R6Class(classname = "ExtraTreesClassifier", inherit = learningmachine::BaseClassifier,
+    public = list(initialize = function(name = "ExtraTreesClassifier", type = "classification",
+        engine = NULL) {
+        self$name <- name
+        self$type <- type
+        self$engine <- engine
+    }, fit = function(X, y, ...) {
+        if (is_package_available("ranger") == FALSE) install.packages("ranger", repos = c(CRAN = "https://cloud.r-project.org"))
+        stopifnot(is.factor(y))
+        private$encoded_factors <- encode_factors(y)
+        private$class_names <- as.character(levels(unique(y)))
+        self$X_train <- X
+        self$y_train <- y
+        self$params <- list(...)
+        self$set_model(fit_func_extratrees_classification(x = self$X_train, y = self$y_train,
+            ...))
+        self$set_engine(list(fit = function(x, y) fit_func_extratrees_classification(x,
+            y, ...), predict = function(obj, X) predict_func_extratrees(obj, X, type = "response")))
+        return(base::invisible(self))
+    }, predict_proba = function(X, ...) {
+        super$predict_proba(X = X, ...)
+    }, predict = function(X, ...) {
+        super$predict(X = X, ...)
+    }))
+
+# 3 - utils -------------------------------------------------------------------
+
+fit_func_extratrees_regression <- function(x, y, ...) {
+    df <- data.frame(y = y, x)  # naming of columns is mandatory for `predict`
+    ranger::ranger(y ~ ., data = df, splitrule = "extratrees", replace = FALSE, sample.fraction = 1, ...)
+}
+
+fit_func_extratrees_classification <- function(x, y, ...) {
+    df <- data.frame(y = y, x)  # naming of columns is mandatory for `predict`
+    ranger::ranger(y ~ ., data = df, splitrule = "extratrees", replace = FALSE, sample.fraction = 1, probability = TRUE, ...)
+}
+
+predict_func_extratrees <- function(obj, newx, ...) {
+    if (is.null(colnames(newx)))
+        colnames(newx) <- paste0("X", 1:ncol(newx))  # mandatory, linked to df in fit_func
+
+    res <- try(predict(object = obj, data = newx, ...)$predictions, silent = TRUE)  # only accepts a named newx
+    if (inherits(res, "try-error")) {
+        res <- try(predict(object = obj, data = matrix(newx, nrow = 1), ...)$predictions,
+            silent = TRUE)
+    }
+    return(res)
+}
diff --git a/R/utils.R b/R/utils.R
index cd6bb32..c146d86 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -101,6 +101,10 @@ my_scale <- function(x, xm = NULL, xsd = NULL) {
 my_scale <- compiler::cmpfun(my_scale)
 
 # prettify summary -----
+if (is_package_available("skimr") == FALSE)
+{
+  utils::install.packages("skimr")
+}
 my_skim <- skimr::skim_with(numeric = skimr::sfl(),
                             base = skimr::sfl(),
                             append = TRUE)
diff --git a/learningmachine.Rproj b/learningmachine.Rproj
index d36470e..97485b5 100644
--- a/learningmachine.Rproj
+++ b/learningmachine.Rproj
@@ -9,7 +9,7 @@ UseSpacesForTab: Yes
 NumSpacesForTab: 2
 Encoding: UTF-8
 
-RnwWeave: Sweave
+RnwWeave: knitr
 LaTeX: pdfLaTeX
 
 BuildType: Package