Mr. DooDoo 90210- > temp contains an 8 point fft. > >>temp = fft(x,num_pts) What's in temp you've printed. What's in num_pnts? > temp = > Columns 1 through 5 > > 0.0000 -0.0000 - 4.0000i 1.4142 + 1.4142i -0.0000 + > 0.0000i -0.0000 > > Columns 6 through 8 > > -0.0000 - 0.0000i 1.4142 - 1.4142i -0.0000 + 4.0000i > > >>angle_fft = angle(temp) > > angle_fft = > > 0 -1.5708 0.7854 1.5965 3.1416 -1.5965 -0.7854 1.5708 > > Qn) the 3 phase angles ( 1.5965 , 3.1416, -1.5965 ) should > actually be equal to zero, since the corresponding temp elements are > (-0.0000 + 0.0000i , -0.0000 , -0.0000 - 0.0000i ) , why is > the angle function returning ( 1.5965 , 3.1416, -1.5965 ) > instead of 0 ? > How to fix this. A "negative zero" looks interesting. If you print that to more precision, my guess is that you find some very small value there. In which case arctan(-small value/zero) would be pi/2. -Jeff |