MATLAB: Exist function returning 0 for a variable that definitely exists

Question

I'm trying to use the 'exist' function to check whether a certain variable has been read in from a .csv file, as the existence of that variable defines the direction the rest of the code should take. This is what I have boils down to:

if exist('DATA.processedData.VTI_EX1048_09_CJC09', 'var')
    CJCConfirm = 'Yes';
else
    CJCConfirm = 'No';
end

(For reasons out of my control, the return has to be 'yes' or 'no'). However, even when running a data set where I know that DATA.processedData.VTI_EX1048_09_CJC09 exists (confirmed by putting it into the command window and seeing it returns a value), this:

exist DATA.processedData.VTI_EX1048_09_CJC09

still returns a 0. I've checked, and the exist function works fine with other variables in my workspace.

What do I need to do differently?

Answer 1

Don't use exist() with struct field syntax. Only use it for variable names. E.g.,

>> a.f = 4
a = 
    f: 4
>> exist('a','var')
ans =
     1
>> exist('a.f','var')
ans =
     0
>> exist('a','var') && isfield(a,'f')
ans =
     1