gnu: Add r-reghelper.

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

gnu/packages/statistics.scm

@@ -7129,3 +7129,25 @@ otting the results.")
        "This package provides a collection of (mostly simple) functions for
 generating and manipulating colors in R.")
       (license license:gpl3))))
+
+(define-public r-reghelper
+  (package
+    (name "r-reghelper")
+    (version "1.1.1")
+    (source (origin
+              (method url-fetch)
+              (uri (cran-uri "reghelper" version))
+              (sha256
+               (base32
+                "0v1987rs6kcpizfhrp3hxsyx9arn5vsbapjfgj9478j73mm844ji"))))
+    (properties `((upstream-name . "reghelper")))
+    (build-system r-build-system)
+    (propagated-inputs (list r-ggplot2 r-lme4 r-mass r-nlme))
+    (home-page "https://github.com/jeff-hughes/reghelper")
+    (synopsis "Helper Functions for Regression Analysis")
+    (description
+     "This package provides a set of functions used to automate commonly used methods
+in regression analysis.  This includes plotting interactions, and calculating
+simple slopes, standardized coefficients, regions of significance (Johnson &
+Neyman, 1936; cf.  Spiller et al., 2012), etc.")
+    (license license:gpl3)))