psd ----> spectrum psd?

2012 2 29
5 个回答
7 次查看（30 天）

0 个投票

Hi
I try to run this prog.
http://www.auditory.org/mhonarc/2000/msg00498.html
du calc. the specific loudness based on the zwicker model.
Whenn I run the prog. i get this back:
"Undefined function 'psd' for input arguments of type 'double'"
the Note in the Editor says
"The function PSD is deprecated. Use SPECTRUM.PSD instead.
What to do?

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回答（5 个）

Honglei Chen
Honglei Chen 2012-2-29

0 个投票

You need to replace psd call with corresponding spectrum.psd code. Here is an example showing how to use spectrum.psd to compute PSD of a signal
Fs = 1000;
t = 0:1/Fs:.3;
x=cos(2*pi*t*200)+randn(size(t));
Hs=spectrum.periodogram;
psd(Hs,x,'Fs',Fs)
More details at http://www.mathworks.com/help/toolbox/signal/ref/spectrum.html
Redkap
Redkap 2012-2-29

0 个投票

thanks for advice, but can't follow you.
this is the m file
% PowSpec.m
%
% Methodology:
%
% Syntax:
% [Yxx,f]=PowSpec(y,fs,df)
%
% Variables:
% INPUT
% y = Time signal
% fs = Sampling frequency
% df = DESIRED df
%
% WORKING
% NFFT = Nummber of points for a given fft
% NOVERLAP = Number of Points to overlap
%
% OUTPUT
% Yxx = Power Spectrum Amplitude
% f = Frequency vector of power spectrum
% Author: Aaron Hastings, Herrick Labs, Purdue University
% Date Started: 11 Nov 00
% Last Revision: 11 Nov 00
% Status: No Known Bugs
function [Yxx,f]=PowSpec(y,fs,df);
%%Want to make sure that we have at least df resolution
NFFT=ceil(fs/df);
%%Set NFFT to power of 2 again err towards higher resolution
NFFT=2^ceil(log2(NFFT));
NOVERLAP=0;
[Yxx,f] = psd(y,NFFT,fs,NFFT,NOVERLAP);
Yxx=2*Yxx/NFFT; %%Scale to get the power spectrum correct
Yxx=Yxx';
return
Honglei Chen
Honglei Chen 2012-2-29

0 个投票

You will replace line
[Yxx,f] = psd(y,NFFT,fs,NFFT,NOVERLAP);
with
hspec = spectrum.welch('OverlapPercent',0,'SegmentLength',NFFT);
hpsd = psd(hspec,y,'NFFT',NFFT,'Fs',fs);
Yxx = hpsd.Data;
f = hpsd.Frequencies
Alternatively, you may also use
[Yxx,f] = pwelch(y,NFFT,0,NFFT,fs);
Redkap
Redkap 2012-3-2

0 个投票

sorry to bother again,
it' still not working:
[Yxx,f]=PowSpec(y,fs,df);
%%Want to make sure that we have at least df resolution
NFFT=ceil(fs/df);
%%Set NFFT to power of 2 again err towards higher resolution
NFFT=2^ceil(log2(NFFT));
NOVERLAP=0;
hspec = spectrum.welch('OverlapPercent',0,'SegmentLength',NFFT);
hpsd = psd(hspec,y,'NFFT',NFFT,'Fs',fs);
Yxx = hpsd.Data;
f = hpsd.Frequencies;
Yxx=2*Yxx/NFFT; %%Scale to get the power spectrum correct
Yxx=Yxx';
return
Undefined variable "spectrum" or class "spectrum.welch".
Error in PowSpec (line 35)
hspec = spectrum.welch('OverlapPercent',0,'SegmentLength',NFFT);
Wayne King
Wayne King 2012-3-2

0 个投票

Hi Redkap, Honglei has been giving you very good advice here. What version of MATLAB are you using and do you have the Signal Processing Toolbox?
If you enter
>>which spectrum.welch
What do you get returned?
Something is wrong if you cannot execute this line:
plot(psd(spectrum.welch,randn(1e3,1)))
Can you copy and paste the above line into your workspace and see what happens?
Also, please tell us your version and make sure:
license('test','signal_toolbox')
returns a 1.
By the way, in:
hspec = spectrum.welch('OverlapPercent',0,'SegmentLength',NFFT);
hpsd = psd(hspec,y,'NFFT',NFFT,'Fs',fs);
Yxx = hpsd.Data;
f = hpsd.Frequencies;
Yxx=2*Yxx/NFFT; %%Scale to get the power spectrum correct
Yxx=Yxx';
You do not need to scale the output of the spectrum objects. That output is already properly scaled to be the PSD estimate so just use hpsd.Data and hpsd.Frequencies

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I have the same problem, and checked the plot(psd(spectrum.welch,randn(1e3,1))) and the license
This is what I get
hspec = spectrum.welch('OverlapPercent',0,'SegmentLength',NFFT);
Error using spectrum.welch (line 52)
what is wrong?
Too many input arguments.

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Redkap
Redkap
2012-2-29

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