Condition for columns based on same index as vector

Question

I'm trying to get a logical matrix as a result of a condition that is specific for each column M(:,i) of the original matrix, based on the value of the same index i in vector N, that is, N(i).

I have looked this up online, but can't find anything quite like it. There must be a simple and clean way of doing this.

M =

     3    -1   100     8
   200     2   300     4
   -10     0     0   400

N =

     4     0    90     7

and my desired solution is, for each column of M(:,i), the values less than N(i):

     1     1     0     0
     0     0     0     1
     1     0     1     0

Answer 1

It's a standard use-case for bsxfun:

O = bsxfun(@lt, M, N)

Here @lt is calling the "less than" function, i.e. it is the function handle to the < operator. bsxfun will then "expand" N along its singleton dimension by applying the function @lt to each row of M and the whole of N.

Note that you can easily achieve the same thing using a for-loop:

O = zeros(size(M));
for row = 1:size(M,1)
    O(row,:) = M(row,:) < N;
end

Or by using repmat:

O = M < repmat(N, size(M,1), 1);

but in MATLAB the bsxfun is usually the most efficient.