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CVS Update
author Daniele Nicolodi <nicolodi@science.unitn.it>
date Tue, 06 Dec 2011 11:09:25 +0100
parents f0afece42f48
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Daniele Nicolodi <nicolodi@science.unitn.it>
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1 function varargout = computepsd(Sxx,Svxx,w,range,nfft,Fs,esttype)
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2 %
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3 % Slight modification of original MATLAB's computepsd to include correct
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4 % scaling for the variance, i.e var(a*x) = a^2*var(x)
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5 %
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6 % VERSION: $Id: computepsd.m,v 1.1 2009/07/22 15:29:59 miquel Exp $
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7 %
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8 % HISTORY: 21-07-09 M Nofrarias
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9 % Creation
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10 %
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11 %%%%%%%%%%%%%%%%%
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12 %
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13 % COMPUTEPSD Compute the one-sided or two-sided PSD or Mean-Square.
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14 % [Pxx,Pvxx,W,UNITS] = COMPUTEPSD(Sxx,Svxx,W,RANGE,NFFT,Fs,ESTTYPE) where the
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15 % inputs and outputs are:
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16 %
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17 % Inputs:
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18 % Sxx - Whole power spectrum [Power]; it can be a vector or a matrix.
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19 % For matrices the operation is applied to each column.
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20 % W - Frequency vector in rad/sample or in Hz.
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21 % RANGE - Determines if a 'onesided' or a 'twosided' Pxx and Sxx are
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22 % returned.
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23 % NFFT - Number of frequency points.
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24 % Fs - Sampling Frequency.
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25 % ESTTYPE - A string indicating the estimate type: 'psd', or 'ms' value.
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26 %
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27 % Outputs:
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28 % Pxx - One-sided or two-sided PSD or MEAN-SQUARE (not scaled by Fs)
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29 % depending on the input arguments RANGE and TYPE.
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30 % W - Frequency vector 0 to 2*Nyquist or 0 to Nyquist depending on
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31 % range, units will be either rad/sample (if Fs is empty) or Hz
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32 % (otherwise).
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33 % UNITS - Either 'rad/sample' or 'Hz'
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34 % Author(s): R. Losada
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35 % Copyright 1988-2005 The MathWorks, Inc.
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36 % $Revision: 1.1 $ $Date: 2009/07/22 15:29:59 $
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37
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38 if nargin < 7
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39 iswinfs = false;
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40 if nargin < 6,
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41 esttype = 'psd';
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42 end
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43 end
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44
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45 w = w(:); % Make sure we always returns a column vector for frequency
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46
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47 % Generate the one-sided spectrum [Power] if so wanted
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48 if strcmp(range,'onesided'),
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49 if rem(nfft,2),
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50 select = 1:(nfft+1)/2; % ODD
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51 Sxx_unscaled = Sxx(select,:); % Take only [0,pi] or [0,pi)
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52 Svxx_unscaled = Svxx(select,:); % Take only [0,pi] or [0,pi)
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53 Sxx = [Sxx_unscaled(1,:); 2*Sxx_unscaled(2:end,:)]; % Only DC is a unique point and doesn't get doubled
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54 Svxx = [Svxx_unscaled(1,:); 4*Svxx_unscaled(2:end,:)];
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55 else
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56 select = 1:nfft/2+1; % EVEN
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57 Sxx_unscaled = Sxx(select,:); % Take only [0,pi] or [0,pi)
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58 Svxx_unscaled = Svxx(select,:); % Take only [0,pi] or [0,pi)
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59 Sxx = [Sxx_unscaled(1,:); 2*Sxx_unscaled(2:end-1,:); Sxx_unscaled(end,:)]; % Don't double unique Nyquist point
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60 Svxx = [Svxx_unscaled(1,:); 4*Svxx_unscaled(2:end-1,:); Svxx_unscaled(end,:)]; % Don't double unique Nyquist point
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61 end
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62 w = w(select);
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63 end
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64
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65 % Compute the PSD [Power/freq]
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66 if ~isempty(Fs),
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67 Pxx = Sxx./Fs; % Scale by the sampling frequency to obtain the psd
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68 Pvxx = Svxx./Fs^2;
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69 units = 'Hz';
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70 else
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71 Pxx = Sxx./(2.*pi); % Scale the power spectrum by 2*pi to obtain the psd
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72 Pvxx = Svxx./(2.*pi)^2;
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73 units = 'rad/sample';
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74 end
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75
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76 if strcmpi(esttype,'ms'),
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77 varargout = {Sxx,Svxx,w,units}; % Mean-square
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78 else
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79 varargout = {Pxx,Pvxx,w,units}; % PSD
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80 end
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81
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82 % [EOF] computepsd.m