🚀 go-pugleaf

Hi

  Can someone explain the relationship between an FFT and an Fourier
Transform.  I am using the FFT command in MatrixX on the following problem:

  x(t) = sin(10*2*Pi*t) + 2*cos(20*2*Pi*t) + 3*sin(30*2*Pi*t)  0 < t < 10.23

and the discrete FFT has magnitudes of 245, 532, and 799 at the 
frequencies 10, 20, and 30 Hz.  If I divide by the number of data points, the
magnitudes drop to .24, .52, and .78.  I would like to recover the magnitudes
of 1, 2, and 3.  Any suggestions, the MatrixX commands are listed below.

J. Vorwald
vorwald@oasys.dt.navy.mil

======================
MatrixX commands
======================
rand('norm');
rand('seed',0);
iend=1024;
tend=10.23;
dt=tend/(iend-1);
t=[0:iend-1]'*dt;
x=sin(10*2*pi*t) ...
  +2*cos(20*2*pi*t) ...
  +3*sin(30*2*pi*t);
xf=fft(x,'hamm')/iend;
hz=[0:iend/2-1]/tend;
plot(hz,abs(xf(1:iend/2)));