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From: "Madhu Shurpali" <madhu.shurpall@cvgrp.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Amplitude in the Frequency Domain
Date: Tue, 10 Feb 2009 13:38:02 +0000 (UTC)
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Thanks Rune for the help. To implement your suggestions in the post, I tried the following script:

t= [0:0.01:9.99];

y= 10*sin(2*pi*t) + 20*sin(2*pi*3*t) + 50*cos(2*pi*5*t);

y1=abs(fftshift(fft(y)));

N_fft = length(t);

F2 = [-N_fft/2: N_fft/2-1]*100/N_fft;

plot(F2, y1);
axis([0 10 0 max(y1)*1.25])

The amplitudes in this case were much bigger that what I expected. Please suggest as to whats diff in this script as compared to your reply. 

Thanks and Regards
Madhu V. Shurpali