From 125e2520f954f96ea8c136afc12e722b3f2811b8 Mon Sep 17 00:00:00 2001
From: dicook <visnut@gmail.com>
Date: Sun, 1 Sep 2024 15:15:23 +1000
Subject: [PATCH] skewness index added

---
 DESCRIPTION             |  2 +-
 NAMESPACE               |  1 +
 NEWS.md                 |  4 ++++
 R/interesting-indices.r | 19 +++++++++++++++++++
 man/tourr-package.Rd    |  1 +
 5 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/DESCRIPTION b/DESCRIPTION
index e62e0b17..91528567 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: tourr
 Title: Tour Methods for Multivariate Data Visualisation
-Version: 1.2.1
+Version: 1.2.2
 Authors@R: c(
     person("Hadley", "Wickham", email = "h.wickham@gmail.com", role = c("aut", "ctb"), comment = c(ORCID = "0000-0003-4757-117X")),
     person("Dianne", "Cook", email = "dicook@monash.edu", role = c("aut", "cre"), comment = c(ORCID = "0000-0002-3813-7155")),
diff --git a/NAMESPACE b/NAMESPACE
index dfd15912..e0c6e112 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -108,6 +108,7 @@ export(search_better_random)
 export(search_geodesic)
 export(search_polish)
 export(search_posse)
+export(skewness)
 export(slice_index)
 export(sphere_data)
 export(splines2d)
diff --git a/NEWS.md b/NEWS.md
index 4cbeb51c..46e3124e 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,7 @@
+# tourr 1.2.2
+
+* New skewness index, as defined in original Cook, Buja, Cabrera paper
+
 # tourr 1.2.1
 
 * anomaly tour is initialised with a random basis
diff --git a/R/interesting-indices.r b/R/interesting-indices.r
index 1eecf72d..9d399e69 100644
--- a/R/interesting-indices.r
+++ b/R/interesting-indices.r
@@ -128,6 +128,25 @@ cmass <- function() {
   }
 }
 
+#' Skewness index.
+#'
+#' Calculates the skewness index. See Cook, Buja and Cabrera (1993)
+#' Projection pursuit indexes based on orthonormal function expansions
+#'  for equations.
+#'
+#' @keywords hplot
+#' @export
+skewness <- function() {
+  function(mat) {
+    n <- nrow(mat)
+    d <- ncol(mat)
+
+    idx <- mean(rowSums(mat * exp(-0.5 * mat^2)))
+
+    idx
+  }
+}
+
 #' LDA projection pursuit index.
 #'
 #' Calculate the LDA projection pursuit index.  See Cook and Swayne (2007)
diff --git a/man/tourr-package.Rd b/man/tourr-package.Rd
index 608bdc6c..33774211 100644
--- a/man/tourr-package.Rd
+++ b/man/tourr-package.Rd
@@ -14,6 +14,7 @@ Implements geodesic interpolation and basis generation functions that allow you
 Useful links:
 \itemize{
   \item \url{https://github.com/ggobi/tourr}
+  \item \url{https://ggobi.github.io/tourr/}
   \item Report bugs at \url{https://github.com/ggobi/tourr/issues}
 }