# randomly select elements of an array

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Noe alvarado on 12 Apr 2012
Commented: Steven Lord on 7 Feb 2022
Hi How i can select randomly elements from a matrix o array
I have the matrix and i want to select "x" numbers of elements
thanks

Walter Roberson on 12 Apr 2012
msize = numel(YourMatrix);
idx = randperm(msize);
YourMatrix(idx(1:x))
If you have a fairly new version of MATLAB, you can instead use
msize = numel(YourMatrix);
YourMatrix(randperm(msize, x))
Walter Roberson on 3 Sep 2021
A{randi(numel(A))}

Prasobhkumar P. P. on 28 Jul 2020
Edited: Walter Roberson on 3 Sep 2021
histHandle= histfit(data,nBins,'normal');
[Val Ind] = max(histHandle(2).YData); %histHandle(2) corresponds to the curve fitted
M = histo18(2).XData(Ind);

Adam Wyatt on 3 Sep 2021
Edited: Adam Wyatt on 3 Sep 2021
Use "randsample"
For array:
Arry = [1 4 5 7 8 9];
Smpl = randsample(Arry, 3)
Smpl = 1×3
9 5 4
For strings:
Arry = ["Yellow" "Green" "Blue" "Orange" "Black" "Grey" "Red" "Brown" "Purple" "White"];
Smpl = randsample(Arry, 2)
Smpl = 1×2 string array
"Purple" "Brown"
How do you want to sample the matrix? If its any element, just convert to array (e.g. Mat(:)). Otherwise you have to apply the function to each row/column separately.
Steven Lord on 7 Feb 2022
See the "Control Random Number Generation" topic on this documentation page.
Some older functions that use random numbers internally (like eigs, which generates a starting point at random if one is not given to it) have the ability to specify inputs that avoid the randomness (in the case of eigs by specifying v0 in the options structure or specifying the StartVector name-value pair argument.)

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