Use significance_of_correlation function in t-test.

[pspp-builds.git] / src / math / correlation.c

diff --git a/src/math/correlation.c b/src/math/correlation.c
index 303b48bcfaccb89098fabaa426f628d50323a2a3..47762747340974f815207389fb48b71a59bf3605 100644 (file)
--- a/src/math/correlation.c
+++ b/src/math/correlation.c
@@ -29,7 +29,12 @@ double
 significance_of_correlation (double rho, double w)
 {
   double t = w - 2;
+
+  /* |rho| will mathematically always be in the range [0, 1.0].  Inaccurate
+     calculations sometimes cause it to be slightly greater than 1.0, so
+     force it into the correct range to avoid NaN from sqrt(). */
   t /= 1 - MIN (1, pow2 (rho));
+
   t = sqrt (t);
   t *= rho;