convnum.m

很多matlab的源代码

function Y =convnum(x,y,dt,ty)
% CONVNUM Numerical convolution.
%
%	Z = CONVNUM(X,Y,DT,TY) numerically convolves vectors X and Y
%	DT = sampling interval (DEFAULT: DT = 1) 
%	TY  = Numerical Integration Algorithm: 
%	TY = 's' for Step or TY = 't' for  Trapezoidal.
%
%	NOTE: If both X and Y are the same size, Z has the same size also.
%	If X is a row vector and Y a column vector, Z is a column vector.
%
%	CONVNUM (with no input arguments) invokes the following example:
%
%	% Compare numerical convolution using Step and Trapezoidal rules 
%	  >>x1=[1 2 3 4],x2=[4 3 2 1]
%	  >>Y1=convnum(x1,x2)
%	  >>Y2=convnum(x1,x2,'t')
%
%         See Also: PAIRSUM, CONVPLOT


% 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 convnum,disp('Strike a key to see results of the example')
pause,x1=[1 2 3 4],x2=[4 3 2 1],
Y1=convnum(x1,x2),Y2=convnum(x1,x2,'t'),return,end

if nargin==3,if isstr(dt),ty=dt;dt=1;else,ty='s';end,end
if nargin==2,ty='s';dt=1;end
[m1 n1]=size(x);[m2 n2]=size(y);
x=x(:);y=y(:);
nx=length(x);ny=length(y);
Y=conv(x,y);
if ty=='t',
m=ny-1;a=y(1)*[x;zeros(m,1)]+y(ny)*[zeros(m,1);x];
b=x(1)*[0;y(2:ny-1,1);zeros(nx,1)]+x(nx)*[zeros(nx,1);y(2:ny-1,1);0];
Y=Y-0.5*(a+b);end
if dt~=1,Y=Y*dt;end,
if m1==1 & m2==1,Y=Y.';end