MATLAB: Dynamic structure reference gives error

dynamic structure reference

I have s structure field named d.NL330260 and a temporary variable grade_n which is a 1×1 cell array containing 'NL330260'. I tried implementing the following:

grade_n = 'NL330260';
d.(grade_n)

but , I get this error message.

Argument to dynamic structure reference must evaluate to a valid field name.

What could be the problem??

Best Answer

This is not the exact code you were using:

grade_n = 'NL330260';
d.(grade_n)

It was more like:

grade_n = {'NL330260'};
d.(grade_n)

When using dynamic field names, the dynamic field name must be a char row vector. You were passing in a scalar cell array with a char row vector inside the cell, but that's different. Using char as you did is one way to resolve the problem; another is to extract the char row vector from the cell.

grade_n = {'NL330260'};
d.(grade_n{1})

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I have no idea what you’re doing, but the way you are doing it is inefficient if not just wrong.

Use a cell array instead:

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      var_a{2} = z(23298:23397);
      var_a{3} = z(93372:93471);
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      var_a{5} = z(206878:206977);

You can then access them easily in a loop.

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There is a way to preallocate memory for a structure in MATLAB 7.6 (R2008a) using the STRUCT and REPMAT commands.

EXAMPLE 1: A structure with two fields

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EXAMPLE 2: A structure with a field with a subfield

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EXAMPLE 3: An array of structures

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http://www.mathworks.com/help/matlab/matlab_prog/memory-requirements-for-a-structure-array.html

Best Answer

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