# How can I store a matrix of varying size in each iteration of a for loop?

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Mathushan Sabanayagam on 2 Aug 2019
Commented: madhan ravi on 2 Aug 2019
Hi,
I have a function that gives an output of a single column, T, and also a matrix Y. The number of columns of Y remains constant but the number of rows changes depending on the input parameter. The number of rows of T also changes depending on the input parameter.
for rho = 500:100:1000
[T Y]= myFunction(rho)
end
I am varying the parameter rho from 500 to 1000, however want to store each iteration in a separate matrix, as I wish to compare the outputs at different rho values. Currently, although all matrix outputs appear in the command window, I cannot store each iteration for further use, only the last iteration at rho=1000 is accessible. I was wondering how this would be possible? Thank you very much for any help as I am a beginner to Matlab.
An example of the output in the command window for one value of rho inputted: Jos (10584) on 2 Aug 2019
Since T and Y are related for a specific value of rho, a struct array is useful here.
rho_range = 500:100:1000 ;
for k = 1:numel(rho_range)
rho = rho_range(k) ;
[data(k).T data(k).Y]= myFunction(rho) ;
end
You might want to pre-allocate the struct array to speed things up. One easy way to do this is to reverse the loop:
for k = numel(rho_range):-1:1
madhan ravi on 2 Aug 2019
Note: Preallocating variables is important.