Mercurial > hg > ishara

diff dsp/dftfmap.m @ 32:c3b0cd708782

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Imported core dsp tools.
author samer
date Sun, 20 Jan 2013 13:48:47 +0000
parents
children
line wrap: on
line diff
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dsp/dftfmap.m	Sun Jan 20 13:48:47 2013 +0000
@@ -0,0 +1,24 @@
+function F=dftfmap(N,Fs)
+% dftfmap - Frequency map for DFT of real signal 
+%
+% dftfmap :: N:natural, real ~'sampling rate' -> dmap(dftbins(N)).
+
+	M=dftbins(N);
+	F=dmap(M,@map,@revmap);
+
+	function I=map(X)
+		I=round(N*X/Fs);
+		I(X<0)=-inf;
+		I(X>Fs/2)=inf;
+	end
+
+	function X=revmap(I)
+		I=shiftdim(shiftdim(I),-1);
+		X1=Fs*(2*I-3)/(2*N);
+		X2=Fs*(2*I-1)/(2*N);
+		X1(I<=1)=0;
+		X2(I>=M)=Fs/2;
+		X=cat(1,X1,X2);
+	end
+end
+