Index: contourc.m
===================================================================
RCS file: /cvs/octave/scripts/plot/contourc.m,v
retrieving revision 1.9
diff -u -r1.9 contourc.m
--- contourc.m	13 Sep 2007 18:22:38 -0000	1.9
+++ contourc.m	8 Oct 2007 22:14:51 -0000
@@ -57,6 +57,7 @@
 ## @end deftypefn
 
 ## Author: shaia
+## Grid mapping contributed by Peter A. Gustafson (2007) and Alexander Barth 
 
 function [c, lev] = contourc (varargin)
 
@@ -90,25 +91,52 @@
     vv = unique (sort (vn));
   endif
 
-  ## Vectorize the x,y vectors, assuming they are output from meshgrid.
-  if (! isvector (x))
-    x = x(1,:);
-  endif
+  if (isvector (x) & isvector (y))
 
-  if (! isvector (y))
-    y = y(:,1);
-  endif
+    ## Make everyone the right dimensions.
+    if (size (x, 2) == 1)
+      x = x';
+    endif
+    if (size (y, 2) == 1)
+      y = y';
+    endif
 
-  ## Make everyone the right dimensions.
-  if (size (x, 2) == 1)
-    x = x';
-  endif
-  if (size (y, 2) == 1)
-    y = y';
+    ## Now call __contourc__ for the real work...
+    c = __contourc__ (x, y, z, vv);
+  else
+    ## Indexes x,y for the purpose of __contourc__.    
+    ii = 1:size (z,2);
+    jj = 1:size (z,1);
+  
+    ## Now call __contourc__ for the real work...
+    c = __contourc__ (ii, jj, z, vv);
+  
+    ## Map the contour lines from index space (i,j) back 
+    ## to the original grid (x,y)
+    i = 1;
+
+    while (i < size (c,2))
+      clen = c(2,i);      
+      ind = i+[1:clen];
+
+      ci = c(1,ind);
+      cj = c(2,ind);
+
+      ## due to rounding errors some elements of ci and cj
+      ## can fall out of the range of ii and jj and interp2 would
+      ## return NA for those values. 
+      ## The permitted range is enforced here: 
+        
+      ci = max(ci,1); ci = min(ci,size(z,2));
+      cj = max(cj,1); cj = min(cj,size(z,1));
+        
+      c(1,ind) = interp2 (ii, jj, x, ci, cj);
+      c(2,ind) = interp2 (ii, jj, y, ci, cj);
+      
+      i = i + clen + 1;
+    endwhile
   endif
-
-  ## Now call __contourc__ for the real work...
-  c = __contourc__ (x, y, z, vv);
+    
   if (nargout == 2)
     lev = vv;
   endif