How to add variables in workspace with names derived from a char array and corresponding values stored in a double array

char array col_names = [time; speed; distance...] and double array data = [0;1;2;3... ,10;20;30;40.. ,5;6;7;8...]. col_names is a mXn matrix and data is a kXm matrix. I need to generate workspace variables time, speed, distance.. with their value content coming from data matrix

[Stephen23]

Magically generating or accessing variable names is how some beginners force themselves into writing slow, complex, buggy code. Read these to know why:

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

https://www.mathworks.com/matlabcentral/answers/414885-is-there-a-simple-way-to-convert-all-fields-of-a-struct-to-local-variables

[harshpurohit11]

Stephen, thanks for the link, however I was not able to make eval work for me for my given problem at hand. I tried doing the following and i got an error saying "scripted assignment dimension mismatch"

for i = 1:length(col_names)

    eval('col_names(i,1:end) = data(:,i)');

end

[James Tursa]

The syntax should have been:

for i = 1:size(col_names,1)
    eval([col_names(i,1:end) ' = data(:,i)']);

BUT ... you are missing the entire point of Stephen's post. This is a very poor programming practice. Read Stephen's link to see why and to discover better methods of writing your code that are easier to read, maintain, etc.

Answer 1

[Honglei Chen]

Here is an example

col_names = ['time ';'speed'];
data = [0 1;2 3;4 5];
for m = 1:2
    eval(sprintf('%s = data(:,m)',col_names(m,:)));
end

HTH

[harshpurohit11]

That gives me an error "Index exceeds matrix dimensions"

[Honglei Chen]

I have no issue running this code. Can you clear your workspace and try again? This is just an example showing how this can be done.

[harshpurohit11]

Thanks Honglei. I had some mis-typing at my end.

Answer 2

[Steven Lord]

Instead of dynamically creating variables, I recommend creating a table array. The variables (columns) in a table are named so you can reference the data using those names.

>> R = randi([-10 10], 15, 3);
>> T = array2table(R, 'VariableNames', {'time', 'speed', 'distance'});
>> T.distance ./ T.time