Chage elements of a matrix

I have created a matrix filled with ones with this;

Matrix = ones(5,4)

And I want to change every second element of the matrix with random values how can I do it?

Answer 1

[Chunru]

Matrix = ones(5,4)

Matrix = 5×4

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

n = numel(Matrix);
Matrix(1:2:n) = randn(size(1:2:n))

Matrix = 5×4

-1.4989 1.0000 -0.9206 1.0000 1.0000 -0.8921 1.0000 1.2853 0.9458 1.0000 0.5612 1.0000 1.0000 -0.4176 1.0000 -0.7999 -0.3232 1.0000 -0.3478 1.0000