Delete element from row, shift the row and add a nan at the end of the row efficiently

Say that we have a matrix A

A =

1 2 3 4 5

5 4 3 2 1

I want to delete number 3 for example in the first row so that I get:

A =

1 2 4 5 nan

5 4 3 2 1

(Please note that the efficiency is the main concern in my question)

Possible solution is:

A(1,:)= [A(1,1:2) A(1,4:5) nan]

However, as my matrix is big, and I want to do this operation frequently, I want to know how I can do this in an efficient way if any?.

thank you.

Answer 1

[Shashank Prasanna]

A = [1 2 3 4 5;5 4 3 2 1];
[~,n] = size(A);

r = 2; % Number to be removed and replaced with nan in the end.

A(1,:) = circshift(A(1,:)',n-r)';
A(1,end) = NaN;

disp(A)

Answer 2

[Jan]

Operating on rows of a matrix is less efficient than on columns, because the processor can access neighboring elements of the RAM faster. Therefore it might be more efficient to transpose the matrix.