Re: pcolor and patch

[Ben Abbott]

On Feb 24, 2010, at 6:41 PM, RENOO wrote:

> 
> Hello,
> 
> This is my first post here as I am starting using Octave and I must confess
> that I am very happy of the quality of this software so far:clap:
> 
> 
> However, there is one feature I can not make.
> 
> I would like to plot my data using a pcolor and then add a patch to hide a
> part of those data. 
> I assumed that using the contourf command is equivalent at finding the
> cordinates of the isoline with the contourc command and then applying the
> patch command.
> 
> So here is a simple example of my script : 
> 
> [X,Y,Z] = peaks(50);
> pcolor(X,Y,Z); shading flat
> hold on
> contourf(X,Y,Z,[1 1],'k')
> 
> error: patch: property value is missing
> error: evaluating if command near line 205, column 3
> error: called from `contourf:parse_args' in file
> `/usr/share/octave/3.0.5/m/plot/contourf.m'                                   
>                                              
> error: called from `contourf' in file
> `/usr/share/octave/3.0.5/m/plot/contourf.m'    
> 
> So I tried without any properties : 
> octave:14> contourf(X,Y,Z,[1 1])                                              
>     
> error: gnuplot (as of v4.2) only supports 2D filled patches
> error: evaluating if command near line 537, column 9
> ....
> 
> google ( and the message error ) told me it comes from gnuplot backend. 
> 
> So I tried from this  http://old.nabble.com/FLTK-howto--td27703703.html post 
> 
> backend("fltk") 
> 
> and this leads me to the following error message : 
> 
> 
> octave3.2:3> [X,Y,Z] = peaks(50);
> octave3.2:4> pcolor(X,Y,Z); shading flat
> octave3.2:5> hold on
> octave3.2:6> contourf(X,Y,Z,[1 1],'k')
> error: mx_el_lt: nonconformant arguments (op1 is 1x2, op2 is 0x0)
> error: evaluating argument list element number 1
> error: evaluating argument list element number 1
> error: called from:
> error:   /usr/share/octave/3.2.2/m/plot/__contour__.m at line 238, column 15
> error:   /usr/share/octave/3.2.2/m/plot/__contour__.m at line 188, column 3
> error:   /usr/share/octave/3.2.2/m/plot/contourf.m at line 73, column 5
> 
> I am running octave 
> octave3.2:6> version
> ans = 3.2.2
> 
> and I also tried with QtOctave version 0.8.1 which runs octave 
> octave:13> version
> ans = 3.0.5
> 
> but in vain.
> 
> Any help  ?

Try contour() instead of contourf(). Does that do what you want?

        [X,Y,Z] = peaks(50);
        pcolor(X,Y,Z); shading flat
        hold on
        contour(X,Y,Z,[1 1],'k')

Ben