Matlab listing: fold.m Next  |  Prev  |  Up  |  Top  |  Index  |  JOS Index  |  JOS Pubs  |  JOS Home  |  Search

## Matlab listing: fold.m

The fold() function ``time-aliases'' the noncausal part of a function onto its causal part. When applied to the inverse Fourier transform of a log-spectrum, it converts non-minimum-phase zeros to minimum-phase zeros. (See §H.11 for an example usage.)

 ``` function [rw] = fold(r) % [rw] = fold(r) % Fold left wing of vector in "FFT buffer format" % onto right wing % J.O. Smith, 1982-2002 [m,n] = size(r); if m*n ~= m+n-1 error('fold.m: input must be a vector'); end flipped = 0; if (m > n) n = m; r = r.'; flipped = 1; end if n < 3, rw = r; return; elseif mod(n,2)==1, nt = (n+1)/2; rw = [ r(1), r(2:nt) + conj(r(n:-1:nt+1)), ... 0*ones(1,n-nt) ]; else nt = n/2; rf = [r(2:nt),0]; rf = rf + conj(r(n:-1:nt+1)); rw = [ r(1) , rf , 0*ones(1,n-nt-1) ]; end; if flipped rw = rw.'; end ```

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