MATLAB: How can i find specified numbers in an array without using for loop

MATLAB

I want to find places of specified values in an defined array but without using for loop since it really slows down my code.

This is just an example of what i have done using for loop,

a=[1 2 3];
b{1}=[1 5 7 9];
b{2}=[-2 0 2 ];
b{3}=[-6 3 9 12 18];
for i=1:length(a)
    answer(i) = find(ismember(b{i},a(i)));
end

I just want to use matlabs built in function or something else instead of using for loop.

Best Answer

solution:

answer=cell2mat(arrayfun(@(x,a) find(ismember(x{:},a)),b,a,'Uni',false))

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MATLAB: Comparing two cell arrays of strings of different sizes

Use strncmp (not strcmp) to make the code simpler. Loop over the smaller cell array B, and pass the larger cell array A whole to strncmp:

A = {'X_ABCDE';'X_BCDEA';'X_BCED'}
B = {'X_A';'X_B'}
%
X = zeros(size(A));
for k = 1:numel(B)
    X(strncmp(A,B{k},3)) = k;
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produces:

>> X
X =
   1
   2
   2

Do not use arrayfun or cellfun if you want fast code: they will be slower than a for-loop.

MATLAB: How to reorder cell array columns based on the order of a vector matrix, while keeping rows intact in Matlab

Would this work?

 >> buffer = arrayfun(@(rId) data(rId,order(rId,:)).', 1:size(order,1), ...
                      'UniformOutput', false) ;
 >> reordered_data = [buffer{:}].'
 reordered_data = 
    'B'    'B'    'B'    'B'    'B'    'A'    'A'    'B'
    'B'    'B'    'A'    'B'    'A'    'A'    'A'    'A'
    'A'    'A'    'B'    'A'    'A'    'B'    'B'    'B'
    'A'    'A'    'A'    'A'    'B'    'A'    'A'    'A'

Best Answer

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MATLAB: Comparing two cell arrays of strings of different sizes

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