Anyway to determine if a variable exists in a mat file (in app designer environment)?

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Pulling hair out trying to find a way to check for the existence of a variable in a 200+MB mat file. I obviously don't want to load into every function and I'm trying to stear clear of the assignin and evalin commands. So far I've tried..
[app.fileName,PathName] = uigetfile('*.mat','MultiSelect','off');
app.fileName = erase(app.fileName,".mat");
m = matfile(app.fileName)
This gives me a 1x1 "" type in the workspace. And when I try to see if a certain variable exists using "exist" or "isfield", I get logical 0. I don't know if there is a way to convert the matfile contents into a list of some sort or if there's a simpler way to check for variables. I can pull the data out of the variable with no problem but when I simply ask if it exists..
if isfield(m,'SomeVariable')
SomeVariable = m.SomeVariable;
if exist('m.SomeVariable','var')
SomeVariable = m.SomeVariable;
Steven Lord
Steven Lord on 10 Jul 2018
The census.mat file contains two variables, cdate and pop.
x = matfile('census.mat');
Does 'cdate' exist in census.mat?
varIsInMat = @(name) ~isempty(who(x, name));
checkcdate = varIsInMat('cdate')
Does 'doesnotexist' exist in census.mat? [I guess I gave that one away.]
checkDNE = varIsInMat('doesnotexist')
Paulo Fonte
Paulo Fonte on 9 Jan 2022
OK. who() works for matfile objects.
But it is rather strange that getfield() works even in nested structs (e,g. getfield(MatfileObj,'Geo','Name'), where . indexing doesn't, but isfield() has not the same behaviour.

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Answers (1)

Steven Lord
Steven Lord on 10 Jul 2018
Use the who or whos methods of your object.


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