gnu: r-gplots: Update to 3.0.4.

* gnu/packages/statistics.scm (r-gplots): Update to 3.0.4.
[native-inputs]: Add r-knitr.

gnu/packages/statistics.scm

@@ -4217,20 +4217,22 @@ (define-public r-gdata
 (define-public r-gplots
   (package
     (name "r-gplots")
-    (version "3.0.3")
+    (version "3.0.4")
     (source
      (origin
        (method url-fetch)
        (uri (cran-uri "gplots" version))
        (sha256
         (base32
-         "0hs6mk48i9yd43rg9wfjc2nxsjjwrnpifxqvxkv8ah18kvpd6xnp"))))
+         "15ip3v4xiqzbanf8bc5fj90cbwdgixr72aj5jrp34jfdzdx0gxwg"))))
     (build-system r-build-system)
     (propagated-inputs
      `(("r-catools" ,r-catools)
        ("r-gdata" ,r-gdata)
        ("r-gtools" ,r-gtools)
        ("r-kernsmooth" ,r-kernsmooth)))
+    (native-inputs
+     `(("r-knitr" ,r-knitr)))
     (home-page "https://cran.r-project.org/web/packages/gplots")
     (synopsis "Various R programming tools for plotting data")
     (description