Hi Urban,
I always use the "pfo.m" script below ("plot faustout") - NOT pretty,
but handy.
- Julius
% input parameters:
if !exist('fs')
fs = 1;
freqstr = 'Normalized Frequency (cycles/sample)';
else
if fs<1000 % (Hack)
freqstr = 'Frequency (kHz)';
else
freqstr = 'Frequency (Hz)';
end
end
if !exist('lwidth')
lwidth = 2; % linewidth for all plots
end
if !exist('kase') % cases to do
% kase = [0 1 0 0]; % log freq
kase = [1 0 0 0]; % linear freq
% kase = [1 1 0 0]; % linear and log freq
% kase = [1 0 1 0]; % linear freq and phase
elseif length(kase)<4
kase = [kase(:)',zeros(1,4-length(kase))];
end
fo = faustout;
x = faustout;
[nx,nchans] = size(x);
N = 2^(nextpow2(nx)+4);
if !exist('Ns')
Ns = N/2+1;
% Ns = round(N*20000/fs); % only look at audio band
end
if !exist('printplots')
printplots = 0;
end
% WINDOW DISABLED
% w = chebwin(nx,300);
% xw = x .* (w * ones(1,nchans));
xw = x;
X = fft(xw,N);
Xs = X(2:Ns,:); % omit dc term; may be multichannel
if !exist('mindb')
mindb = -200;
end
Xsdb = db(Xs,mindb);
f = fs*[1:Ns-1]/N;
if kase(1) % dB magnitude vs. linear freq
figure(2);
plot(f,Xsdb,'linewidth',lwidth);
ylabel('Magnitude (dB)');
xlabel(freqstr);
grid('on');
if exist('pfx') && nchans>1, dolegend(pfx,nchans,1); end
if printplots
print -depsc -F:12 './pfo-magdb-c.eps';
print -deps -F:12 -mono -solid './pfo-magdb.eps';
end
end
if kase(2) % log-log
figure(3);
semilogx(f,Xsdb,'linewidth',lwidth);
%axis([10 20000 ymin ymax])
ylabel('Magnitude (dB)');
xlabel(freqstr);
grid('on');
if exist('pfx') && nchans>1, dolegend(pfx,nchans,3); end
if printplots
print -depsc -F:12 './pfo-magdb-semilog-c.eps';
print -deps -F:12 -mono -solid './pfo-magdb-semilog.eps';
end
end
if kase(3) % phase delay
aXs = unwrap(angle(Xs));
Xspd = - aXs ./ ((2*pi*f'/fs)*ones(1,nchans));
figure(4);
plot(f,Xspd,'linewidth',lwidth);
% semilogx(f,Xspd);
ylabel('Phase Delay (samples)');
xlabel(freqstr);
grid('on');
if exist('pfx') && nchans>1, dolegend(pfx,nchans,1); end
if printplots
print -depsc -F:12 './pfo-pd-c.eps';
print -deps -F:12 -mono -solid './pfo-pd.eps';
end
end
if kase(4) % group delay
aXs = unwrap(angle(Xs));
Xspd = -diff(aXs);
Xspd = [0,Xspd(:)'];
figure(4);
plot(f,Xspd,'linewidth',lwidth);
% semilogx(f,Xspd);
ylabel('Group Delay (samples)');
xlabel(freqstr);
grid('on');
if exist('pfx') && nchans>1, dolegend(pfx,nchans,1); end
if printplots
print -depsc -F:12 './pfo-gd-c.eps';
print -deps -F:12 -mono -solid './pfo-gd.eps';
end
end
At 08:59 AM 9/12/2013, urban wrote:
>Hi,
>
>I learned that I can view the frequency response of a filter like this:
>
>octave:1> plot(20*log10(abs(fft(faustout,1024))(1:512,:)));
>
>
>
>but how do I get the frequency axis to display Hz(log) ?
>
>Can someone provide me with a octave script?
>
>
>Thanks,
>Urban
>
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Professor of Music and, by courtesy, Electrical Engineering
CCRMA, Stanford University
http://ccrma.stanford.edu/~jos/
------------------------------------------------------------------------------
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1. Consolidate legacy IT systems to a single system of record for IT
2. Standardize and globalize service processes across IT
3. Implement zero-touch automation to replace manual, redundant tasks
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