Thread Subject: does fft process give values?

Hye everyone...

I want to ask....let say if i had some codes such as:

%compute fft for image 1

xx1 = fr; % Signal
yy1 = fft(xx1); % Compute DFT of x
m1 = abs(yy1); % Magnitude
p1 = unwrap(angle(yy1)); % Phase
f1 = (0:length(yy1)-1)*99/length(yy1);% Frequency vector
axes(handles.axes1);
plot(f1,m1); title('Magnitude');
set(gca,'XTick',[20 40 60 80]);
set(gca,'YTick',[20 40 60 80]);
axes(handles.axes2);
plot(f1,p1*180/pi); title('Phase');
set(gca,'XTick',[15 40 60 85]);


Does fft process gives a values (in integer) for the equ m1 = abs
(yy1);?

thanks...

Hi, Not really sure what your question "Does fft process gives a values (in integer) for the equ m1 = abs> (yy1);?" means exactly, but..if you are asking will m1=abs(fft(signal)); always be an integer, the answer is no. It will rarely if ever be an integer. The DFT of a signal will be complex-valued, so when you take the absolute value, you're getting the square root of the sum of the real part squared plus the imaginary part squared. The result at any given frequency will very rarely be an integer.

hope that helps,
wayne

islinaismail@gmail.com wrote in message <07f708ad-b864-45a4-af66-6b51130d771b@q33g2000pra.googlegroups.com>...
> Hye everyone...
>
> I want to ask....let say if i had some codes such as:
>
> %compute fft for image 1
>
> xx1 = fr; % Signal
> yy1 = fft(xx1); % Compute DFT of x
> m1 = abs(yy1); % Magnitude
> p1 = unwrap(angle(yy1)); % Phase
> f1 = (0:length(yy1)-1)*99/length(yy1);% Frequency vector
> axes(handles.axes1);
> plot(f1,m1); title('Magnitude');
> set(gca,'XTick',[20 40 60 80]);
> set(gca,'YTick',[20 40 60 80]);
> axes(handles.axes2);
> plot(f1,p1*180/pi); title('Phase');
> set(gca,'XTick',[15 40 60 85]);
>
>
> Does fft process gives a values (in integer) for the equ m1 = abs
> (yy1);?
>
> thanks...

On Apr 10, 3:59=A0pm, "Wayne King" <wmkin...@gmail.com> wrote:
> Hi, Not really sure what your question "Does fft process gives a values (=
in integer) for the equ m1 =3D abs> (yy1);?" means exactly, but..if you are=
 asking will m1=3Dabs(fft(signal)); always be an integer, the answer is no.=
 It will rarely if ever be an integer. The DFT of a signal will be complex-=
valued, so when you take the absolute value, you're getting the square root=
 of the sum of the real part squared plus the imaginary part squared. The r=
esult at any given frequency will very rarely be an integer.
>
> hope that helps,
> wayne

Oh..i see...but,what value did i get from it?how to calculate it?tq...