initialization.m

function R = initialization(X, init)
[d,n] = size(X);
if isstruct(init)  % initialize with a model
    R  = expectation(X,init,InU,InV);
elseif length(init) == 1  % random initialization
    k = init;
    idx = randsample(n,k);
    m = X(:,idx);
    [~,label] = max(bsxfun(@minus,m'*X,dot(m,m,1)'/2),[],1);
    [u,~,label] = unique(label);
    while k ~= length(u)
        idx = randsample(n,k);
        m = X(:,idx);
        [~,label] = max(bsxfun(@minus,m'*X,dot(m,m,1)'/2),[],1);
        [u,~,label] = unique(label);
    end
    R = full(sparse(1:n,label,1,n,k,n));
elseif size(init,1) == 1 && size(init,2) == n  % initialize with labels
    label = init;
    k = max(label);
    R = full(sparse(1:n,label,1,n,k,n));
elseif size(init,1) == d  %initialize with only centers
    k = size(init,2);
    m = init;
    [~,label] = max(bsxfun(@minus,m'*X,dot(m,m,1)'/2),[],1);
    R = full(sparse(1:n,label,1,n,k,n));
else
    error('ERROR: init is not valid.');
end