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view m-toolbox/classes/+utils/@math/computeDftPeriodogram.m @ 19:69e3d49b4b0c database-connection-manager
Update ltpda_uo.fromRepository
author | Daniele Nicolodi <nicolodi@science.unitn.it> |
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date | Mon, 05 Dec 2011 16:20:06 +0100 |
parents | f0afece42f48 |
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% COMPUTEDFTPERIODOGRAM compute periodogram with dft %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % DESCRIPTION % % Define one sided periodogram as: % Xp(f) = 2*T*|DFT(w(t)*x(t))/T|^2 % Where w(t) are window sameples, which are supposed to be square % integrable: sum(w(t)^2)=1 % % CALL % Sf = computeDftPeriodogram(x,fs,f,order,win,psll) % Sf = computeDftPeriodogram(x,fs,f,order,win,[]) % % % INPUT % % - x, data series, Nx1 double % - fs, sampling frequency Hz, 1x1 double % - f, frequenci vector Hz, 1x1 double % - order, detrend order, -1,0,1,2,3,4,... % - win, window name. e.g 'BH92' % - psll, for Kaiser window only % % REFERENCES % % D. B. Percival and A. T. Walden, Spectral Analysis for Physical % Applications (Cambridge University Press, Cambridge, 1993) p 291. % % L Ferraioli 28-03-2011 % % $Id: computeDftPeriodogram.m,v 1.2 2011/03/29 15:36:43 luigi Exp $ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% function Sf = computeDftPeriodogram(x,fs,f,order,win,psll) % detrend segment if order < 0 xd = x; % no detrend else [xd,coeffs] = ltpda_polyreg(x,order); end N = numel(x); % get window switch lower(win) case 'kaiser' wnd = specwin('Kaiser', N, psll); otherwise wnd = specwin(win, N); end w = wnd.win; w = w./sqrt(wnd.ws2); % compensates for the power of the window. if size(w)~=size(xd) w = w.'; end % apply window xdw = xd.*w; T = 1/fs; Nf = numel(f); Sf = zeros(Nf,1); for ii=1:Nf xx = utils.math.dft(xdw,f(ii),T); xx = xx/T; Sf(ii) = 2*T*xx*conj(xx); end end