Hi, I am new to Numpy, and would like to start by translating a (badly written?) piece of MATLAB code. What I have come up with so far is this: px = np.zeros_like(tmp_px); py = np.zeros_like(tmp_py); pz = np.zeros_like(tmp_pz) w = np.zeros_like(tmp_w) x = np.zeros_like(tmp_x); y = np.zeros_like(tmp_y); z = np.zeros_like(tmp_z) j=-1 for i in range(tmp_px.size): if tmp_px[i] > 2: j += 1 px[j] = tmp_px[i] py[j] = tmp_py[i] pz[j] = tmp_pz[i] w[j] = tmp_w[i] x[j] = tmp_x[i] y[j] = tmp_y[i] z[j] = tmp_z[i] px=px[:j+1]; py=py[:j+1]; pz=pz[:j+1] w=w[:j+1] x=x[:j+1]; y=y[:j+1]; z=z[:j+1] It works, but I'm sure it's probably the most inefficient way of doing it. What would be a decent rewrite? Thank you so much, Best regards, Andrei