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ltpda_pwelch

PURPOSE ^

LTPDA_PWELCH makes power spectral density estimates of the time-series objects

SYNOPSIS ^

function varargout = ltpda_pwelch(varargin)

DESCRIPTION ^

 LTPDA_PWELCH makes power spectral density estimates of the time-series objects

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

 DESCRIPTION: LTPDA_PWELCH makes power spectral density estimates of the
              time-series objects in the input analysis objects.

 CALL:       b = ltpda_pwelch(a1,a2,a3,...,pl)

 INPUTS:     b    - output analysis objects
             aN   - input analysis objects
             pl   - input parameter list

             Makes PSD estimates using ltpda_psd() of each input AO.

             If the last input argument is a parameter list (plist) it is used.
             The following parameters are recognised.

 PARAMETERS: 'Win'   - a specwin window object [default: Kaiser -200dB psll]
             'Olap' - segment percent overlap [default: taken from window function]
             'Nfft'  - number of samples in each fft [default: length of input data]
             'Scale' - one of 
                                'ASD' - amplitude spectral density
                                'PSD' - power spectral density [default]
                                'AS'  - amplitude spectrum
                                'PS'  - power spectrum
             'Order' - order of segment detrending
                        -1 - no detrending
                         0 - subtract mean [default]
                         1 - subtract linear fit
                         N - subtract fit of polynomial, order N  

 VERSION:    $Id: ltpda_pwelch.html,v 1.14 2008/03/31 10:27:39 hewitson Exp $

 HISTORY:    07-02-2007 M Hewitson
                Creation

 The following call returns a parameter list object that contains the
 default parameter values:

 >> pl = ltpda_pwelch('Params')
 
 The following call returns a string that contains the routine CVS version:

 >> version = ltpda_pwelch('Version')

 The following call returns a string that contains the routine category:

 >> category = ltpda_pwelch('Category')

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CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SUBFUNCTIONS ^

SOURCE CODE ^

0001 function varargout = ltpda_pwelch(varargin)
0002 % LTPDA_PWELCH makes power spectral density estimates of the time-series objects
0003 %
0004 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0005 %
0006 % DESCRIPTION: LTPDA_PWELCH makes power spectral density estimates of the
0007 %              time-series objects in the input analysis objects.
0008 %
0009 % CALL:       b = ltpda_pwelch(a1,a2,a3,...,pl)
0010 %
0011 % INPUTS:     b    - output analysis objects
0012 %             aN   - input analysis objects
0013 %             pl   - input parameter list
0014 %
0015 %             Makes PSD estimates using ltpda_psd() of each input AO.
0016 %
0017 %             If the last input argument is a parameter list (plist) it is used.
0018 %             The following parameters are recognised.
0019 %
0020 % PARAMETERS: 'Win'   - a specwin window object [default: Kaiser -200dB psll]
0021 %             'Olap' - segment percent overlap [default: taken from window function]
0022 %             'Nfft'  - number of samples in each fft [default: length of input data]
0023 %             'Scale' - one of
0024 %                                'ASD' - amplitude spectral density
0025 %                                'PSD' - power spectral density [default]
0026 %                                'AS'  - amplitude spectrum
0027 %                                'PS'  - power spectrum
0028 %             'Order' - order of segment detrending
0029 %                        -1 - no detrending
0030 %                         0 - subtract mean [default]
0031 %                         1 - subtract linear fit
0032 %                         N - subtract fit of polynomial, order N
0033 %
0034 % VERSION:    $Id: ltpda_pwelch.html,v 1.14 2008/03/31 10:27:39 hewitson Exp $
0035 %
0036 % HISTORY:    07-02-2007 M Hewitson
0037 %                Creation
0038 %
0039 % The following call returns a parameter list object that contains the
0040 % default parameter values:
0041 %
0042 % >> pl = ltpda_pwelch('Params')
0043 %
0044 % The following call returns a string that contains the routine CVS version:
0045 %
0046 % >> version = ltpda_pwelch('Version')
0047 %
0048 % The following call returns a string that contains the routine category:
0049 %
0050 % >> category = ltpda_pwelch('Category')
0051 %
0052 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0053 
0054 ALGONAME = mfilename;
0055 VERSION  = '$Id: ltpda_pwelch.html,v 1.14 2008/03/31 10:27:39 hewitson Exp $';
0056 CATEGORY = 'Signal Processing';
0057 
0058 % Initialise output
0059 bs = [];
0060 
0061 %% Check if this is a call for parameters, the CVS version string
0062 % or the function category
0063 if nargin == 1 && ischar(varargin{1})
0064   in = char(varargin{1});
0065   if strcmp(in, 'Params')
0066     varargout{1} = getDefaultPL();
0067     return
0068   elseif strcmp(in, 'Version')
0069     varargout{1} = VERSION;
0070     return
0071   elseif strcmp(in, 'Category')
0072     varargout{1} = CATEGORY;
0073     return
0074   end
0075 end
0076 
0077 % Collect input ao's, plist's and ao variable names
0078 in_names = {};
0079 for ii = 1:nargin
0080   in_names{end+1} = inputname(ii);
0081 end
0082 [as, pls, invars] = collect_inputs(varargin, in_names);
0083 na = length(as);
0084 
0085 % Loop over input AOs
0086 for j=1:na
0087 
0088   % Unpack AO
0089   a = as(j);
0090   d = a.data;
0091 
0092   if isa(a, 'ao')
0093     % check input data
0094     if isa(d, 'tsdata')
0095 
0096       % combine plists
0097       plo = combine(pls, getDefaultPL());
0098 
0099       % check all defaults are sensible
0100       Nfft = find(plo, 'Nfft');   % Number of points in each fft
0101       setWindow = 0;
0102       if Nfft <= 0
0103         Nfft = length(d.y);
0104         disp(sprintf('! Using default Nfft of %g', Nfft))
0105         setWindow = 1;
0106       end
0107       plo = pset(plo, 'Nfft', Nfft);
0108 
0109       Win = find(plo, 'Win');   % Window object
0110       if setWindow || length(Win.win)~=Nfft
0111         switch Win.name
0112           case {'Kaiser', 'Flattop'}
0113             Win = specwin(Win.name, Nfft, Win.psll);
0114           otherwise
0115             Win = specwin(Win.name, Nfft);
0116         end
0117         disp(sprintf('! Reset window to %s(%d)', strrep(Win.name, '_', '\_'), length(Win.win)))
0118       end
0119       plo = pset(plo, 'Win', Win);
0120 
0121       Olap = find(plo, 'Olap');   % Amount to overlap each fft
0122       if Olap <= 0
0123         Olap = Win.rov;
0124         disp(sprintf('! Using default overlap of %2.1f%%', Olap))
0125       end
0126       plo = pset(plo, 'Olap', Olap);
0127 
0128       % Get detrending order
0129       order = find(plo, 'Order');
0130       
0131       % scaling of spectrum
0132       scale = find(plo, 'Scale');
0133       
0134       % check parameters
0135       if length(Win.win) ~= Nfft
0136         error('### Window length should be same as Nfft.');
0137       end
0138 
0139       % Compute PSD using pwelch
0140       [f, pxx, info] = ltpda_psd(d.y, Win.win, round(Olap/100*Nfft), Nfft, d.fs, scale, d.yunits, order);
0141       
0142       % create new output fsdata
0143       fs = fsdata(f, pxx, d.fs);
0144       fs = set(fs, 'name', sprintf('%s(%s)', scale, d.name));
0145       fs = set(fs, 'yunits', info.units);
0146       fs = set(fs, 'enbw', Win.nenbw*d.fs/Nfft);
0147       fs = set(fs, 'navs', info.navs);
0148 
0149       % create new output history
0150       h = history(ALGONAME, VERSION, plo, a.hist);
0151       h = set(h, 'invars', invars);
0152 
0153       % make output analysis object
0154       b = ao(fs, h);
0155 
0156       % set name
0157       if na~=length(invars) || isempty(invars{j})
0158         nj = a.name;
0159       else
0160         nj = invars{j};
0161       end
0162       b = setnh(b, 'name', sprintf('%s(%s)', scale, nj));
0163 
0164       % add to outputs
0165       bs = [bs b];
0166 
0167     else
0168       warning('### Ignoring input AO number %d (%s); it is not a time-series.', j, a.name)
0169     end
0170   end
0171 end % loop over analysis objects
0172 
0173 % set output
0174 varargout{1} = bs;
0175 
0176 
0177 %--------------------------------------------------------------------------
0178 % Get default params
0179 function plo = getDefaultPL()
0180 
0181 plo = plist('Nfft', -1, ...
0182   'Win', specwin('Kaiser', 1, 200), ...
0183   'Olap', -1, ...
0184   'Scale', 'PSD',...
0185   'Order', 0);
0186 
0187 
0188

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