@proxify<EOL>def columns(x, rho, proxop):
xnext = np.zeros_like(x)<EOL>for ix in range(x.shape[<NUM_LIT:1>]):<EOL><INDENT>xnext[:, ix] = proxop(x[:, ix], rho)<EOL><DEDENT>return xnext<EOL>
Applies a proximal operator to the columns of a matrix