store vectors from a for loop in a matrix

I have this function

 for ci=0.0001:0.5:(2*alt_Col)

    Esi=0.003*((ci-di)/(ci))  
end

where di is a column vector. How do I store all the Esi vector in a matrix? Thanks in advance

Answer 1

[Walter Roberson]

You can use the following pattern when you are using a for loop over a range of non-integral values:

 ci_vals = 0.0001:0.5:(2*alt_Col);
 num_ci = length(ci_vals);
 num_di = length(di);
 Esi = zeros(num_ci, num_di);
 for ci_idx = 1 : num_ci;
    ci = ci_vals(ci_idx);
    Esi(ci_idx, :) = 0.003*((ci-di) ./ (ci)); 
 end

... Or you could omit the for loop, and use a vectorized approach:

ci = 0.0001:0.5:(2*alt_Col);
Esi = 0.003 * bsxfun(@rdivide, bsxfun(@minus, ci, di), (ci));

Or you could use:

ci = 0.0001:0.5:(2*alt_Col);
[CI, DI] = meshgrid(ci, di);
Esi =  0.003 * ((CI-DI) ./ (CI));

or, in R2016b or later, you can use built-in implicit expansion:

ci = 0.0001:0.5:(2*alt_Col);
Esi = 0.003 * ((ci-di) ./ (ci));

The bxsfun version is a more efficient approach than meshgrid. The implicit expansion version "aims" to be more efficient than the bsxfun but user tests have shown that sometimes the implicit expansion version is slower than the bsxfun version.

[Camilo Granda]

Thanks a lot Walter!