How do I use IF-loops with plot_handles?

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fxo on 20 May 2013
I'm having a bit of a problem to integrate the if-loop with plot handles. So the program I'm writing has this structure:
It has this menufile in which you choose what you want to do (This is only a small part of it):
case 1
plot_handles = createPlot(plot_handles);
case 2
In case 1 you'll be able to index a figure and write the function which is plotted and you're being returned to the menu.
function plot_handles = createPlot(plot_handles)
figureid = input('Input figure-ID: ');
func= input('Input function f(x): ','s');
error('Nonvalid function!');
Back in the menu I enter case 2 where the thought is that it'll ask you which figure you want to edit.Once you've choosen that you're supposed to be able to edit that figures' linewidth:
function changeWidth(plot_handles)
figureid = input('Input figure-ID: ');
h = plot_handles(figureid);
if exist(figureid)== 0 % Here's the problem, I don't know how to test if ...
% the ID is correct or not.
error('Invalid figure-ID')
width=input('Input new width: ');
set(h, 'linewidth', width)
The problem is that I don't know how to check if figure-ID is correct in the IF-loop, elsewhere I want the errormessage so be written out.
Would really appreciate some help!

Accepted Answer

per isakson
per isakson on 20 May 2013
Edited: per isakson on 20 May 2013
"check if figure-ID is correct "
There is a function:
Test for valid graphics object handle
I think code cells are useful when experimenting with code, see Evaluate Subsections of Files Using Code Cells. One small step at a time, check the result and proceed to next step.
Doc says:
h = ezplot(...) returns the handle to all the plot objects in h.
My first step:
h = ezplot( @sin );
get( h, 'Type' )
ans =
Thus, ezplot returned the handle of the line object. Did you expect that?
per isakson
per isakson on 20 May 2013
"right way" that depends on who you ask. I doubbt.
  • I hessitate to use the same variable, h, as handle to a graphic object and index to a double array.
  • I hessitate to rely on current figure and current axes when more than one figure or axes exist simultaneously.

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