matlab vectorization if statement

Can someone please tell me the vectorized implementation of following matlab code. Predicted is an array containing either of the two values "pos" or "neg". I have to copy the values when condition comes true.

    p = 1;
    box = zeros(size(bbox));


   for k = 1: size(predicted)
        if predicted(k) == 'pos'
            box(p,:) = bbox(k,:);
            p = p + 1;
        end
   end