MATLAB: How to use a loop to isolate column vectors of a matrix into separate variables

evalforvariablesxlsread

What I'm trying to do is strip the columns from an excel file into separate variables for analysis. I know how to do it if I know the number of columns, then I can do it manually. What i would like is to do it using a for loop. This is what I have so far:

 data = xlsread(fullfile(path,file));
 N = size(data,2);
 M = size(data,1);
 for i = 1:N
     varname = strcat('data',num2str(i));
     eval(sprintf('%s = %f',varname,data(:,i))); 
 end

any help would be greatly appreciated.

Thanks, George

Best Answer

The answer is "Don't do that!!!"

See the FAQ for why it's a_bad_idea (tm) and alternatives...

http://matlab.wikia.com/wiki/FAQ#Why_is_it_advised_to_avoid_using_the_.22eval.22_function.3F

http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F

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MATLAB: Generate variable names and assign them to workspace variables

This is the answer to the question you've asked:

 generated_variable_name = 'Big_whatever'; %(needs to be in your working workspace
 eval([generated_variable_name ' = 5;'])
 evalin('base',[generated_variable_name ' = 5;']);
 assignin('base',generated_variable_name, 5)

The right answer is to use a structure or a cell array, as it is WAY more generic:

 structure(2).filename  = 'p12_13_50'
 structure(2).aerofoils = [12 13];
 structure(2).blending  = 50;
 structure(2).data      = ...
 cell{2}{1} = 'p12_13_50';
 cell{2}{2} = [12 13];
 cell{2}{3} = [50];
 cell{2}{4} = .... ;

MATLAB: For cycle to extract row of an Array and save them into vectors

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

https://www.mathworks.com/help/matlab/matlab_prog/string-evaluation.html

Best Answer

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MATLAB: Generate variable names and assign them to workspace variables

MATLAB: For cycle to extract row of an Array and save them into vectors

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