assigning images to appdata and checking if exists

After saving an image IM into appdata using

img=setappdata(0,IM,'pic')

I want to be able to check if this field 'pic' exists later. The reason is that I haver radio buttons that autoscale an image and I only want them to perform the autoscale routine if the image has been saved into memory using appdata.

Later when I retrieve the image by:

img=getappdata(0,'pic')

If the image isn't there,then I don't want the autoscale routine to continue (as it has nothing to autoscale and crashes)

I have tried:

isfield(0,'pic')
but this didn't work.

Is there another way to check whether the IM has already been assigned the 'pic'

Thanks Jason

Answer 1

[Adam]

isappdata(h,name)

should work for this, h being 0 in your case I guess, name being 'pic'.

As an aside, I don't use appdata myself except on rare occasions, but I would have thought you would want to set the appdata of your figure, not the root object.