building matrix of a variable series in a for loop

hi all...i have some variables with their values in workspace, lets say y1,y2....y9.

I want to convert this array in to 3 x 3 matrix such that [y1 y2 y3; y4 y5 y6; y7 y8 y9]..automatically. So that next time if i have values like, y1,y2,..........y49, some script automatically builds a matrix [y1,y2...y7; y8,y8....y14;....and so on]

thanks in advance

[Geoff Hayes]

m - if your variables are named y1, y2, etc., then initialize your 3x3 matrix as

 A = [y1 y2 y3; y4 y5 y6; y7 y8 y9];

Though I suspect that isn't really what you want as you mention string to num in your question title. Please clarify.

[Geoff Hayes]

m - why not just create the matrix of values instead of creating individual variables? Much easier to manage that way and less prone to error.

[m naveed]

thanks for your comments,,,,i am building a simulink model with many subsystems in it with each subsystem consisting of many to workspace blocks, which i managed to name y1,y2, and so on depending on the number of iteration i want. And i want to arrange this data in the form of matrices in matlab for further manipulation. Now say, subsystem 1 of my model have elements y1,y2,...y9. next time i might have elements y1,y2....,y49. so i want to automatically build the matrix where i should only eneter some number and it is automatically built. it doesnt matter whether its the values of y1, y2 etc or variables, y1, y2 etc...thanks once again, seems like there is no rocket science in it but i am stuck at this. need some help

[m naveed]

never mind...found the solution.

evalin('base', (['y', num2str(i)])); does the job

[Stephen23]

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

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

Answer 1

[Andrei Bobrov]

a = rand(21);

n = numel(a);
m = ceil(sqrt(n));
out = reshape([a(:);nan(m^2-n,1)],m,[])';