# HG changeset patch
# User Rik <rik@octave.org>
# Date 1354310475 28800
# Node ID d803cd07f31a0d52c06024020c3e7d57749c54da
# Parent  242e9efd43154fb4537f76b15373f5337449d6cc
Tweak C++ implementation of jet colormap to produce exactly the same result as jet.m

* graphics.cc (jet_colormap): Create the index entry x in the same manner as
linspace so that jet_colormap() produces the same results as jet.m.

diff --git a/libinterp/interpfcn/graphics.cc b/libinterp/interpfcn/graphics.cc
--- a/libinterp/interpfcn/graphics.cc
+++ b/libinterp/interpfcn/graphics.cc
@@ -137,6 +137,10 @@
 {
   Matrix cmap (64, 3, 0.0);
 
+  // Produce X in the same manner as linspace so that 
+  // jet_colormap and jet.m produce *exactly* the same result.
+  double delta = 1.0 / 63.0;
+
   for (octave_idx_type i = 0; i < 64; i++)
     {
       // This is the jet colormap.  It would be nice to be able
@@ -146,7 +150,7 @@
       // called, so calling an interpreted function is not
       // possible.
 
-      double x = i / 63.0;
+      double x = i*delta;
 
       if (x >= 3.0/8.0 && x < 5.0/8.0)
         cmap(i,0) = 4.0 * x - 3.0/2.0;