MATLAB: Error “Matrix index is out of range for deletion” with dynamic variable names but not hardcoded names

dynamic variablematrix index is out of range for deletion

I get the error for the following case using dynamic variables:
        % some things I pulled out of my data for the example:
        arms = {'L','R'};
        fields.L = [17 8 12 16];
        fields.R = [12,6];
        [~,removeL,removeR] = intersect(fields.L,fields.R);
        uniquefields = fields;
        % loop through arms (errors here)
        for iArm = 1:length(arms)
            uniquefields.(arms{iArm})(['remove',arms{iArm}]) = [];
        end
But it doesn't happen when I hardcode it:
        uniquefields.L(removeL) = [];
        uniquefields.R(removeR) = [];
Does anyone know how to fix it? Thanks for any help!

Best Answer

The code blocks are not doing the same thing. Your loop is doing:
uniquefields.('L')('removeL') = []
It could be fixed with an eval of the string but that is going in the wrong direction. I suggest trying this sequence:
 arms = {'L','R'};
 fields.L = [17 8 12 16];
 fields.R = [12,6];
 [~,remove{1},remove{2}] = intersect(fields.L,fields.R);
 uniquefields = fields;
 % loop through arms 
 for iArm = 1:length(arms)
   uniquefields.(arms{iArm})(remove{iArm}) = [];
 end
There are probably much better solutions for your final code I don't much like needing a list of field names to be used dynamically.
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