Mercurial > hg > octave-lyh
changeset 8667:a89198168175
freqz.m: freqz.m: fix for long input
author | Ben Abbott <bpabbott@mac.com> |
---|---|
date | Wed, 04 Feb 2009 11:37:49 -0500 |
parents | 34b7b93f91bc |
children | 739b0aebf261 |
files | scripts/ChangeLog scripts/signal/freqz.m |
diffstat | 2 files changed, 32 insertions(+), 8 deletions(-) [+] |
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--- a/scripts/ChangeLog +++ b/scripts/ChangeLog @@ -1,3 +1,8 @@ +2009-02-04 Frederick Umminger <Frederick_Umminger@playstation.sony.com> + + * signal/freqz.m: Ensure causal phase response. + Handle long input correctly. + 2009-02-04 Petr Mikulik <mikulik@physics.muni.cz> * plot/__go_draw_axes__.m: Pass "interpolate 0, 0" to gnuplot
--- a/scripts/signal/freqz.m +++ b/scripts/signal/freqz.m @@ -127,19 +127,38 @@ k = max (length (b), length (a)); hb = polyval (postpad (b, k), exp (j*w)); ha = polyval (postpad (a, k), exp (j*w)); - elseif (strcmp (region, "whole")) - f = Fs * (0:n-1)' / n; + else ## polyval(fliplr(P),exp(jw)) is O(p n) and fft(x) is O(n log(n)), ## where p is the order of the polynomial P. For small p it ## would be faster to use polyval but in practice the overhead for ## polyval is much higher and the little bit of time saved isn't ## worth the extra code. - hb = fft (postpad (b, n)); - ha = fft (postpad (a, n)); - else - f = Fs/2 * (0:n-1)' / n; - hb = fft (postpad (b, 2*n))(1:n); - ha = fft (postpad (a, 2*n))(1:n); + k = max (length (b), length (a)); + if (k > n/2 && nargout == 0) + ## Ensure a causal phase response. + n = n * 2 .^ ceil (log2 (2*k/n)); + endif + + if (strcmp (region, "whole")) + N = n; + else + N = 2*n; + endif + + f = Fs * (0:n-1).' / N; + + pad_sz = N*ceil (k/N); + b = postpad (b, pad_sz); + a = postpad (a, pad_sz); + + hb = zeros (n, 1); + ha = zeros (n, 1); + + for i = 1:N:pad_sz + hb = hb + fft (postpad (b(i:i+N-1), N))(1:n); + ha = ha + fft (postpad (a(i:i+N-1), N))(1:n); + endfor + endif h = hb ./ ha;