How do I use IF-loops with plot_handles?

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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
changeWidth(plot_handles);
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)
clc
try
figureid = input('Input figure-ID: ');
func= input('Input function f(x): ','s');
figure(figureid);
h=ezplot(func);
plot_handles(figureid)=h;
catch
lasterr
error('Nonvalid function!');
end
end
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')
else
width=input('Input new width: ');
set(h, 'linewidth', width)
end
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:
ishandle
Test for valid graphics object handle
Continue:
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' )
returns
ans =
line
Thus, ezplot returned the handle of the line object. Did you expect that?
  3 Comments
fxo
fxo on 20 May 2013
I solved it on my own using ishandle as you said, once again, thank you for the waypointer!
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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