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How can I check if a variable exists within another variable?

Asked by Raymond Mo on 8 Jul 2019
Latest activity Commented on by Raymond Mo on 8 Jul 2019
I have a temp variable that changes depending on the type of data being processed. I want to check if that temp variable contains a field called sig or a field called SI. I've written the code below:
if exist('temp.sig','var') ~= 0 %checks if line or map
N = normalize(temp.sig);
image(app.UIAxes,N);
handles.isLine = true;
%display line
elseif exist('temp.SI','var') ~= 0
N = normalize(temp.SI(1,:,:));
image(app.UIAxes,N)
else
end
The issue is that whenever I run this it immediately evaluates both statements to false, even though one or the other should be true. It seems as if the exist statement doesn't check within the temp variable for SI or sig, it just looks for the names in the workspace. I don't know what the issue is or how to fix it.

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2 Answers

Answer by Walter Roberson
on 8 Jul 2019
 Accepted Answer

if isfield(temp, 'sig')
N = normalize(temp.sig);
image(app.UIAxes,N);
handles.isLine = true;
elseif isfield(temp, 'SI')
N = normalize(temp.SI(1,:,:));
image(app.UIAxes,N)
end

  1 Comment

Thanks for the quick answer! It works :)

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Answer by John D'Errico
on 8 Jul 2019

It fails, because exist does not apply to fields of a strcture.
help isfield
isfield True if field is in structure array.

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