# How to replace all the ones in a matrix with the string 'hey'?

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oshawcole on 4 Dec 2017
Commented: Walter Roberson on 6 Dec 2017
matrix= [1 0 0.1 0.001 4; 5.9 2.1 3.15 8.95 1.11]
All the ones should be replaced with 'hey'
This is my code
matrix= [1 0 0.1 0.001 4; 5.9 2.1 3.15 8.95 1.11];
matrix= num2str(matrix);
matrix(matrix=='1') = 'h'
when I replace 'h' with 'hey' it gives me this error
matrix(matrix=='1') = 'hey'

Walter Roberson on 5 Dec 2017
newmatrix = num2cell(matrix);
newmatrix(matrix == 1) = {'hey'};
Walter Roberson on 6 Dec 2017
It is possible to do in one line, but it gets so messy that it is not recommended.
Here is a way to do it with the assistance of a helper function.
IDXAT = @(M,IDX) M(IDX);
disp(IDXAT(cat(3,num2cell(matrix),repmat({'hey'},size(matrix))), reshape(1:numel(matrix), size(matrix))+numel(matrix)*(abs(matrix)==1)))
The output would look like
'hey' [ 0] 'hey' [0.001] [ 4]
[5.9] 'hey' [3.15] 'hey' [1.11]
I am not sure that is acceptable to you.

John D'Errico on 4 Dec 2017
You can't. A matrix is composed of numbers. You cannot insert a string for some elements, replacing an arbitrary numeric element.

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