# HG changeset patch
# User Jaroslav Hajek <highegg@gmail.com>
# Date 1271358607 -7200
# Node ID e74bff13aa26bdb96a4c572f239cfc1e4715b496
# Parent  6538ff56294975865bb7e285f9f294fa5aa73b4a
improve stdnormal_cdf accuracy by using erfc (bug #29543)

diff --git a/scripts/ChangeLog b/scripts/ChangeLog
--- a/scripts/ChangeLog
+++ b/scripts/ChangeLog
@@ -1,3 +1,7 @@
+2010-04-15  Jaroslav Hajek  <highegg@gmail.com>
+
+	* statistics/distributions/stdnormal_cdf.m: Calculate using erfc.
+
 2010-04-13  David Bateman  <dbateman@free.fr>
 
 	* statistics/discrete_cdf.m: Reimplement using lookup.
diff --git a/scripts/statistics/distributions/stdnormal_cdf.m b/scripts/statistics/distributions/stdnormal_cdf.m
--- a/scripts/statistics/distributions/stdnormal_cdf.m
+++ b/scripts/statistics/distributions/stdnormal_cdf.m
@@ -37,7 +37,7 @@
     error ("stdnormal_cdf: x must not be empty");
   endif
 
-  cdf = (ones (sz) + erf (x / sqrt (2))) / 2;
+  cdf = erfc (x / (-sqrt(2))) / 2;
 
 endfunction