只把這個函數給你吧,你自己保存下:
function F = ztrans(varargin)
%ZTRANS Z-transform.
%? ?F = ZTRANS(f) is the Z-transform of the scalar sym f with default
%? ?independent variable n.??The default return is a function of z:
%? ?f = f(n) => F = F(z).??The Z-transform of f is defined as:
%? ?? ?F(z) = symsum(f(n)/z^n, n, 0, inf),
%? ?where n is f's symbolic variable as determined by FINDSYM.??If
%? ?f = f(z), then ZTRANS(f) returns a function of w:??F = F(w).
%
%? ?F = ZTRANS(f,w) makes F a function of the sym w instead of the
%? ?default z:??ZTRANS(f,w) <=> F(w) = symsum(f(n)/w^n, n, 0, inf).
%
%? ?F = ZTRANS(f,k,w) takes f to be a function of the sym variable k:
%? ?ZTRANS(f,k,w) <=> F(w) = symsum(f(k)/w^k, k, 0, inf).
%
%? ?Examples:
%? ?? ?syms k n w z
%? ?? ?ztrans(2^n)? ?? ?? ???returns??z/(z-2)
%? ?? ?ztrans(sin(k*n),w)? ? returns??sin(k)*w/(1-2*w*cos(k)+w^2)
%? ?? ?ztrans(cos(n*k),k,z)??returns??z*(-cos(n)+z)/(-2*z*cos(n)+z^2+1)
%? ?? ?ztrans(cos(n*k),n,w)??returns??w*(-cos(k)+w)/(-2*w*cos(k)+w^2+1)
%? ?? ?ztrans(sym('f(n+1)')) returns??z*ztrans(f(n),n,z)-f(0)*z
%
%? ?See also IZTRANS, LAPLACE, FOURIER.
%? ?Copyright 1993-2003 The MathWorks, Inc.
%? ?$Revision: 1.20.4.2 $??$Date: 2004/04/16 22:23:22 $
% Trap for errors in input first.
if nargin >= 4
error('symbolic:sym:ztrans:errmsg1','ZTRANS can take at most 3 input variables');
end
% Make f a sym and extract the variable closest to 'x'.
f = sym(varargin{1});
% Find all symbolic variables in f.
vars = [ '{' findsym(f) '}' ];
% Determine whether n is in the expression.
varcheck = maple([ vars ' intersect {n}']);
% If n is a symbolic variable, make it the default.??Otherwise
% let the variable closest to x be the variable of integration.
if isequal(varcheck,'{n}')
var = sym('n');
else
var = findsym(f,1);
end
% If var is empty, then the default is var = 'n'.
if isempty(var)
var = sym('n');
end
% determine whether f is a function of z or another variable.
z_test = strcmp(char(var),'z');
%? ?If f = f(z), return F = F(w)
if nargin == 1 & z_test == 1
n = var;
z = 'w';
end
if nargin == 1 & z_test == 0
n = var;
z = 'z';
end
if nargin == 2
n = var;
if isempty(n), n = 'n'; end;
z = sym(varargin{2});
end
if nargin == 3
n = sym(varargin{2});
z = sym(varargin{3});
end
F = maple('map','ztrans',f,n,z);
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