Merge pull request #125 from symengine/fix/cran-vignette-check

fix cran check issues and bump version to 0.2.6

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: symengine
 Title: Interface to the 'SymEngine' Library
-Version: 0.2.4
+Version: 0.2.6
 Authors@R: c(person("Jialin", "Ma", email="[email protected]", role = c("cre", "aut")),
              person("Isuru", "Fernando", email="[email protected]", role = c("aut")),
              person("Xin", "Chen", email="[email protected]", role = c("aut")))
@@ -35,6 +35,7 @@ Encoding: UTF-8
 LazyData: true
 URL: https://github.com/symengine/symengine.R
 BugReports: https://github.com/symengine/symengine.R/issues
+Additional_repositories: https://Marlin-Na.github.io/drat
 License: GPL (>= 2)
 Copyright: The R package bundles the 'SymEngine' library source and its subcomponents
     under 'src/upstream' directory. See file COPYRIGHTS for retained copyright notices

R/dxdt.R

@@ -72,7 +72,7 @@ setMethod("show", signature = c(object = "DxdtOde"),
 #' @rdname ODESystem
 #' @export
 #' @examples
-#' \donttest{
+#' \dontrun{
 #' ## Lorenz system
 #' use_vars(x, y, z)
 #' sigma <- 10

vignettes/odesystem.Rmd

@@ -19,6 +19,11 @@ body {
 }
 </style>
 
+```{r, eval=TRUE, include=FALSE}
+if (!all(sapply(c("odeintr"), requireNamespace, quietly = TRUE)))
+  knitr::opts_chunk$set(eval = FALSE)
+```
+
 [odeintr](https://github.com/thk686/odeintr) by Timothy H. Keitt is an R package for
 integrating differential equations with the
 [Boost odeint library](https://headmyshoulder.github.io/odeint-v2/).