MATLAB: Delete some matrix elements

delete element

I want to delete the elements that are larger than a certain value, then the next element will replace the deleted one(shift forward). For example,
[1 2 9;
3 1 4;
2 9 7]
, delete those larger than 4, the output will be
[1 2 3;
1 4 2]
If the no. of elements is not the multiple of 3, the remaining ones will be deleted. Could anyone give me some ideas? Thanks everyone!

Best Answer

The way to delete elements of an array that fulfill a given condition such as greater than is with:
 A(A > value) = [];
So in your case:
 A(A > 4) = [];
Note that with a matrix, it will flatten it into a column vector, as there's no guarantee it deletes enough element to keep the same number of columns (or rows, or whatever dimension you want to stay the same).
For example, what matrix would you want if you started with
 A = [1 2 9; 3 1 4; 2 2 7];
If you know that the number of elements deleted is always going to produce a valid rectangular matrix with the same number of columns as you started with, the following would work:
 ncol = size(A, 2);
 A(A > 4) = [];
 A = reshape(A, [], ncol); %will error if the number of elements remaining in A is not a multiple of ncol
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