只把这个函数给你吧,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);