mk_stochastic.m

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function T = mk_stochastic(T)
% MK_STOCHASTIC Ensure the argument is a stochastic matrix, i.e., the sum over the last dimension is 1.
% T = mk_stochastic(T)
%
% If T is a vector, it will sum to 1.
% If T is a matrix, each row will sum to 1.
% If T is a 3D array, then sum_k T(i,j,k) = 1 for all i,j.

% Set zeros to 1 before dividing
% This is valid since S(j) = 0 iff T(i,j) = 0 for all j

if (ndims(T)==2) & (size(T,1)==1 | size(T,2)==1) % isvector
  T = normalise(T);
elseif ndims(T)==2 % matrix
  S = sum(T,2); 
  S = S + (S==0);
  norm = repmat(S, 1, size(T,2));
  T = T ./ norm;
else % multi-dimensional array
  ns = size(T);
  T = reshape(T, prod(ns(1:end-1)), ns(end));
  S = sum(T,2);
  S = S + (S==0);
  norm = repmat(S, 1, ns(end));
  T = T ./ norm;
  T = reshape(T, ns);
end