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it looks like a bug, which could be linked to the fact that even if
Xr(11:12)==[0 0], Xr(11:12) are complex number for scilab (try
isreal(Xr(11:12))).<br>
<br>
are you trying to get the phase of thoses complex numbers?<br>
if yes, i suggest you to use something like
imag(log(Xr(11:12)+%eps)) as a crapy workaround (instead of
atan(imag(xr),real(xr)))<br>
<br>
<br>
<br>
Le 10/05/2011 14:38, Laurent Berger a écrit :
<blockquote cite="mid:4DC931D4.5090902@univ-lemans.fr" type="cite">In
this program
<br>
<br>
clear;
<br>
N=256;
<br>
n=0:N-1;
<br>
Xr=zeros(1,N);
<br>
f0=2;
<br>
Xr(f0+1)=1/(2*%i);
<br>
Xr(N-(f0+1)+2)=-1/(2*%i);
<br>
Xr=Xr.*exp(%i*%pi*2*6*n/N);
<br>
xr=ifft(Xr);
<br>
disp (atan(imag(Xr(11:12)),real(Xr(11:12))))
<br>
disp (Xr(11)-Xr(12))
<br>
<br>
results are
<br>
0. 3.1415927
<br>
<br>
0
<br>
<br>
<br>
I don't understand why two numbers with a difference of 0 can have
a numerical phase of 0 or pi .
<br>
In matlab results are
<br>
0 0
<br>
0
<br>
<br>
<br>
!Scilab Version: 5.3.1.1299160056 !
<br>
! !
<br>
!Operating System: Windows XP 5.1 !
<br>
! !
<br>
!Java version : 1.6.0_18 !
<br>
! !
<br>
!Java runtime information : Java(TM) SE Runtime Environment
(build 1.6.0_18-b07) !
<br>
! !
<br>
!Java vm information : Java HotSpot(TM) Client VM (build
16.0-b13, mixed mode) !
<br>
! !
<br>
!Vendor specification: Sun Microsystems Inc. !
<br>
</blockquote>
<br>
<br>
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