How to quickly save a matrix by adding rows?

Dear All,

I calculate a row Ai and save it in my defined matrix A using the following way:

A = [A; Ai];

But I foud it took a lot of time. Is there a faster way?

Thanks a lot.

Benson

[Stephen23]

"Is there a faster way?"

https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html

Answer 1

[dpb]

Yes. Preallocate the array and index into it...without context it's conjecture what you have/are doing, but the general idea is

A=zeros(max(variable_i),size(A,2));     % preallocate A as array of zeros
for i=1:max(variable_i)                 % for the loop size each i
  % whatever to compute Ai
  ...
  A(i,:) = Ai;                          % store the new row in A
end

The above will not show degradation in speed as i increases.