gnu: Add r-xnomial.

* gnu/packages/statistics.scm (r-xnomial): New variable.

gnu/packages/statistics.scm

@@ -1828,6 +1828,34 @@ documents (including DTDs), both local and accessible via HTTP or FTP.  Also
 offers access to an XPath \"interpreter\".")
     (license license:bsd-2)))
 
+(define-public r-xnomial
+  (package
+    (name "r-xnomial")
+    (version "1.0.4")
+    (source
+     (origin (method url-fetch)
+             (uri (cran-uri "XNomial" version))
+             (sha256
+              (base32
+               "1mwx302576rmsjllbq2clfxilm3hkyp5bw0wmwqbn0kgv5wpy8z6"))))
+    (properties (quasiquote ((upstream-name . "XNomial"))))
+    (build-system r-build-system)
+    (home-page "http://cran.r-project.org/web/packages/XNomial")
+    (synopsis "Goodness-of-Fit test for multinomial data")
+    (description
+     "This package provides an exact Goodness-of-Fit test for
+multinomial data with fixed probabilities.  It can be used to
+determine whether a set of counts fits a given expected ratio.  To see
+whether a set of observed counts fits an expectation, one can examine
+all possible outcomes with @code{xmulti()} or a random sample of them
+with @code{xmonte()} and find the probability of an observation
+deviating from the expectation by at least as much as the observed.
+As a measure of deviation from the expected, one can use the
+log-likelihood ratio, the multinomial probability, or the classic
+chi-square statistic.  A histogram of the test statistic can also be
+plotted and compared with the asymptotic curve.")
+    (license (list license:gpl2+ license:gpl3+))))
+
 (define-public r-lambda-r
   (package
     (name "r-lambda-r")