Octave also has new-style colorOrderIndex

Tests for `verLessThan('matlab', ...)` give an error on Octave.
Use a helper function to check which platform we're on it.
This particular "new graphics mode" was added around Octave 8, but
but Chebfun only works on Octave >= 11 so no need for specific Octave
version checks.

Author: cbm755

@chebfun/plot.m

@@ -302,8 +302,16 @@
 
 %% Plotting starts here:
 
+% For plotting, it's useful to know whether we're running in old or new
+% Matlab graphics mode
+if ( is_octave() || ~verLessThan('matlab', '8.4') )
+    newGraphicsMode = true;
+else
+    newGraphicsMode = false;
+end
+
 % Acquire initial color cycle if running R2014b+.
-if ( ~compatible_verLessThan('matlab', '8.4') )
+if ( newGraphicsMode )
     if ( ~holdState )
         set(gca, 'ColorOrderIndex', 1);
     end
@@ -318,7 +326,7 @@
 hold on
 
 % Get color cycle prior to point plot if running R2014b.
-if ( ~compatible_verLessThan('matlab', '8.4') )
+if ( newGraphicsMode )
     newColorOrder = get(gca, 'ColorOrderIndex');
     set(gca, 'ColorOrderIndex', originalColorOrder)
 end
@@ -333,7 +341,7 @@
 end
 
 % Reset color cycle prior to jump plot if running R2014b.
-if ( ~compatible_verLessThan('matlab', '8.4') )
+if ( newGraphicsMode )
     set(gca, 'ColorOrderIndex', originalColorOrder);
 end
 
@@ -366,7 +374,7 @@
 end    
 
 % Reset colors prior to legend data plot if running R2014b.
-if ( ~compatible_verLessThan('matlab', '8.4') )
+if ( newGraphicsMode )
     set(gca, 'ColorOrderIndex', originalColorOrder);
 end
 
@@ -387,7 +395,7 @@
 end
 
 % Reset colors prior to legend data plot if running R2014b.
-if ( ~compatible_verLessThan('matlab', '8.4') )
+if ( newGraphicsMode )
     set(gca, 'ColorOrderIndex', newColorOrder);
 end
 
@@ -445,15 +453,21 @@
 %PLOTDELTAS   Plots delta functions.
     h = [];
 
+    if ( is_octave() || ~verLessThan('matlab', '8.4') )
+        newGraphicsMode = true;
+    else
+        newGraphicsMode = false;
+    end
+
     % Get and save the current ColorOrder if running on R2014a or earlier.
-    if ( compatible_verLessThan('matlab', '8.4') )
+    if ( ~newGraphicsMode )
         originalColorOrder = get(gca, 'ColorOrder');
         colorOrder = circshift(originalColorOrder, 1);
     end
 
     for k = 1:1:numel(deltaData)
         % Set color for the next delta function plot.
-        if ( compatible_verLessThan('matlab', '8.4') )
+        if ( ~newGraphicsMode )
             % Manually manipulate the ColorOrder for R2014a or earlier.
             colorOrder = circshift(colorOrder, -1);
             set(gca, 'ColorOrder', colorOrder);
@@ -466,7 +480,7 @@
     end
 
     % Restore the ColorOrder if running on R2014a or earlier.
-    if ( compatible_verLessThan('matlab', '8.4') )
+    if ( ~newGraphicsMode )
         set(gca, 'ColorOrder', originalColorOrder);
     end
 end

@separableApprox/waterfall.m

@@ -37,7 +37,7 @@
 
 % For plotting, it's useful to know whether we're running in old or new
 % Matlab graphics mode
-if ( ~verLessThan('matlab', '8.4') )
+if ( is_octave() || ~verLessThan('matlab', '8.4') )
     newMatlabVersion = true;
 else
     newMatlabVersion = false;