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11 cze 2012 · For a given matrix A, the straightforward approach with the for loop would be: [N, M] = size(A); B = zeros(sum(1:N), M); offset = 1; for i = 1:N B(offset:offset + N - i, :) = A(i:end, :); offset = offset + size(A(i:end, :), 1); end B is the desired output matrix. However, this solution is expected to be slow as well, because of the for loop.
As pointed out in a few other answers, you can iterate over all elements in a matrix A (of any dimension) using a linear index from 1 to numel(A) in a single for loop. There are also a couple of functions you can use: arrayfun and cellfun. Let's first assume you have a function that you want to apply to each element of A (called my_func).
Use functions instead of scripts. Functions are generally faster. Prefer local functions over nested functions. Use this practice especially if the function does not need to access variables in the main function. Use modular programming. To avoid large files and files with infrequently accessed code, split your code into simple and cohesive ...
27 maj 2022 · It is certainly possible to iterate over data values directly (the FOR operator does not care what kind of array you give it to iterate over), but in general with MATLAB it is simpler and easier to iterate over the array size (i.e. indices) rather than iterating over data, because invariably those indices will also be required in multiple ...
21 mar 2015 · Edited: Stephen23 on 21 Mar 2015. Although you have not given any details at all of your code, there are several ways you can speed up your code: use vectorized code rather than loops. preallocate arrays before loops. use logical indexing rather than subscripts. do not change a variable's data class.
25 lip 2014 · There are some speed optimisations which are obvious in matlab: always pre-allocate your array; use implicit vector notation if possible; don’t set loop indexes or tests which require the creation of large arrays every loop iteration
16 maj 2012 · To preallocate a cell-array we can use the cell function (explicit preallocation), or the maximal cell index (implicit preallocation). Explicit preallocation is faster than implicit preallocation, but functionally equivalent (Note: this is contrary to the experience with allocation of numeric arrays and other arrays):
