www.gusucode.com > symbolic工具箱matlab源码程序 > symbolic/@sym/fourier.m
function F = fourier(f,varargin) %FOURIER Fourier integral transform. % F = FOURIER(f) is the Fourier transform of the symbolic expression % or function f with default independent variable x. If f does not % contain x, then the default variable is determined by SYMVAR. % By default, the result F is a function of w. If f = f(w), then F % is returned as a function of the variable v, F = F(v). % % By definition, F(w) = c*int(f(x)*exp(s*i*w*x),x,-inf,inf). % % You can set the parameters c,s to any numeric or symbolic values % by setting the preference SYMPREF('FourierParameters',[c,s]). % By default, the values are c = 1 and s = -1. % % F = FOURIER(f,v) returns F as a function of the variable v % instead of the default variable w: % F(v) = c*int(f(x)*exp(s*i*v*x),x,-inf,inf). % % F = FOURIER(f,u,v) treats f as a function of the variable u instead % of the default variable x: % F(v) = c*int(f(u)*exp(s*i*v*u),u,-inf,inf). % % Examples: % syms t v w x f(x) % fourier(1/t) returns -pi*sign(w)*1i % fourier(exp(-x^2),x,t) returns pi^(1/2)*exp(-t^2/4) % fourier(exp(-t)*heaviside(t),v) returns 1/(1+v*1i) % fourier(diff(f(x)),x,w) returns w*fourier(f(x),x,w)*1i % % See also SYM/IFOURIER, SYM/LAPLACE, SYM/ZTRANS, SUBS, SYMPREF. % Copyright 2011 The MathWorks, Inc. F = transform('fourier', 'x', 'w', 'v', f, varargin{:}); end