corrp.m

很多matlab的源代码

function Y =corrp(x,y,dt)
% CORRP Periodic correlation.
%
%	Y = CORRP(X,Y,dt) Periodic correlation of arrays X and Y 
%	dt = Sampling interval dt [Default: dt = 1].
%
%	NOTE: 	Rxy = Corr(X,Y) = conv(X, fliplr(Y))
%		Ryx = Corr(Y,X) = conv(Y, fliplr(X)) 
%
%       CORRP (with no input arguments) invokes the following example:
%
%	% Find the autocorrelation of f1 = [1 2 3 4].
%       >>f1 = [1 2 3 4]
%       >>Y1 = corrp(f1,f1,0.5)


% ADSP Toolbox: Version 2.0 
% For use with "Analog and Digital Signal Processing", 2nd Ed.
% Published by PWS Publishing Co.
%
% Ashok Ambardar, EE Dept. MTU, Houghton, MI 49931, USA
% http://www.ee.mtu/faculty/akambard.html
% e-mail: [e-mail]
% Copyright (c) 1998


if nargin==0,
 help corrp
 disp('Strike a key to see results of the example')
 pause
 f1 = [1 2 3 4]
 Y1 = corrp(f1,f1,0.5)
 return
end

nx = length(x);
ny = length(y);
if nx ~= ny,
 error('vectors must be same length')
end

x = x(:).';
y = y(:).';
%y = [y(1) fliplr(y(2:ny))]; %Create circularly folded y
%%%%%% CHANGE TO MATCH FFT RESULTS %%%%%%%%%%%%%%%%%%%
y = [fliplr(y(2:ny)) y(1)]; %Create circularly folded y

Y = conv(x,conj(y));
Y = [conj(Y) 0];
Y = Y(1:nx)+Y(nx+1:2*nx);
if nargin == 3, Y = Y*dt; end