MATLAB: How to change values in a 2 dimensional vector at random points

logical indexingvector operations

Lets say I have n*m matrix. For each row I would pick a random starting point and change the values from that point to the end of the row.
x=ones(n,m);
T=randsample(m,n); %starting points for each row
End=m*ones(size(T)); %ending points for each row 
x(:,T:End)=0 %This doesn't work but something like that
Eg:
magic(5);
T=randsample(5,5);
T =
       2
       3
       1
       5
       4
  %Now I want to make every value from T to end in X=0
  for i=1:5
    x(i,T(i):end)=0
  end
Is there a way to vectorize this. If I'm simulating a million trials using a for loop is not very efficient.

Best Answer

This might use too much memory, but it's worth a try:
c = meshgrid(1:m, 1:n);  % size(x) is [n m], not [m n]
change = bsxfun(@gt, c, T);
x(change) = newVal;
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