function Y=apply_house(Y,v,tau)
%apply_house applies a householder transformation
%
% Z=apply_house(Y,v,tau) computes Z=(I-tau*v*v')*Y, where Z is of the same
%   size as Y, Y has as many rows as v, v is a vector, and tau is a scalar.

Y=Y-v*(tau*(v'*Y));