I have a 1D array (say A) of size N (i.e N x 1; N-rows, 1 Column). Now I want to create an array of size N x 2 (N-rows, 2-columns) with the array A as one column and the other column with a same element (0 in the given example below).
For e.g If
A =[1;2;3;4;5];
I'd like to create a matrix B which is
B=[0 1; 0 2; 0 3; 0 4; 0 5]
How do I do this in Matlab?
You can also abuse bsxfun for a one-liner -
bsxfun(@times,[0,1],A)
Or matrix-multiplication for that implicit expansion -
A*[0,1]
bsxfun(@plus,A*[0,1],[22,0]). But for efficiency, I would suggest using @Suever's answer by initializing with B = 22*ones(numel(A), 2); and then B(:,2) = A;. Or just concatenate : B = [22*ones(numel(A),1) A].You can initialize B to be an Nx2 array of all zeros and then assign the second column to the values in A.
A = [1;2;3;4;5];
B = zeros(numel(A), 2);
B(:,2) = A;
% 0 1
% 0 2
% 0 3
% 0 4
% 0 5
If you actually just want zeros in that first column, you don't even have to initialize B as MATLAB will automatically fill in the unknown values with 0.
% Make sure B isn't already assigned to something
clear B
% Assign the second column of uninitialized variable B to be equal to A
B(:,2) = A;
You can try this approach
B=[zeros(length(A),1) A]
