[manual] suggested addition to pcolor description

[Francesco Potorti`]

>However, in Matlab there clearly is (as the color interpolates across  
>each patch). Each rectangle of the mesh is interpreted as a pair of  
>triangles and the color is linearly interpolated across it.

I see.  Thank you.  Probably this explanation should go into the
documentation for `shading'.

Maybe with a note saying that the gnuplot backend does not implement
"interp".

>> Yes, but what is essential, and is not mentioned, is that if C is 3x3,
>> pcolor draws a picture with 4 (2x2) rectangles, because the 3x3 values
>> of C are intended to be at the mesh vertices.  This is not documented
>> anywhere.  On the other hand, imagesc, which does a very similar job,
>> draws instead a picture with 9 (3x3) rectangles, because the values of
>> its argument are intended to be in the middle of the mesh rectangles
>> (not at the vertices).  In my opinion, it is well worth noting the
>> similarities and differences between the two in the manual; I only
>> discovered them after quite some time doing experiments.
>
>I was unware of those features. Can you post a simple example? Perhaps  
>you can modify the one I provided above?

It is simpler by using less points.  Just try this:

  pcolor(magic(3)); shading("flat")

gives you four (2x2) patches.  On the other hand,

  imagesc(magic(3)); axis("xy")

gives you nine (3x3) patches.