gnu: Add r-vioplot.

* gnu/packages/cran.scm (r-vioplot): New variable.

gnu/packages/cran.scm

@@ -1402,3 +1402,23 @@ Data Analysis---The Kernel Approach with S-Plus Illustrations', Oxford
 University Press.  It provides smoothing methods for nonparametric regression
 and density estimation")
     (license license:gpl2+)))
+
+(define-public r-vioplot
+  (package
+    (name "r-vioplot")
+    (version "0.2")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (cran-uri "vioplot" version))
+       (sha256
+        (base32
+         "16wkb26kv6qr34hv5zgqmgq6zzgysg9i78pvy2c097lr60v087v0"))))
+    (build-system r-build-system)
+    (propagated-inputs `(("r-sm" ,r-sm)))
+    (home-page "http://wsopuppenkiste.wiso.uni-goettingen.de/~dadler")
+    (synopsis "Violin plot")
+    (description
+     "This package provides a violin plot, which is a combination of a box
+plot and a kernel density plot.")
+    (license license:bsd-3)))