matlab多项式7M文件举例.doc

M文件举例本章说明了在精通MATLAB工具箱 中两个函数。这些函数说明了本章所论述的多项式概念和如何写M文件函数。关于M文件的更多信息，参阅第8章。在讨论M文件函数的内部结构之前，我们考虑这些函数做些什么。 n%earlier datan =0.000010.000020.0000 b%earlier datab =-20-140-320-260 mmpsim(n)%strip away negligible leading termans =10.000020.0000 mmp2str(b)%convert polynomial to stringans =-20s3 - 140s2 - 320s1 - 260 mmp2str(b , x )ans =-20x3 - 140x2 - 320x1 - 260 mmp2str(b , , 1)ans =-20*(s3 + 7s2 + 16s1 + 13) mmp2str(b , x , 1)ans =-20*(x3 + 7x2 + 16x1 + 13)这里函数mmpsim删除在多项式n中近似为零的第一个系数。函数mmp2str把数值多项式变换成等价形式的字符串表达式。该两个函数的主体是：function y=mmpsim(x,tol)%MMPSIM Polynomial Simplification,Strip Leading Zero Terms.%MMPSIM(A) Delets leading zeros and small coefficients in the %polynomial A(s). Coefficients are considered small if their %magnitude is less than both one and norm(A)*1000*eps.%MMPSIM(A,TOL) uses TOL for its smallness tolerance.%Copyright (c) 1996 by Prentice-Hall,Inc.if nargin2, tol=norm(x)*1000*eps; endx=x(:). ;%make sure input is a row i=find(abs(x).99&abs(x)tol) ;%find insignificant indicesx(i)=zeros(1, length(i) ;%set them to zeroi=find(x=0) ;%find significant indicesif isempty(i)y=0 ;%extreme case: nothing left!elsey=x(i(1) : length(x) ;%start with first termend%and go to end of polynomialfunction s=mmp2str(p,v,ff)%MMP2STR Polynomial Vector to String Conversion.%MMP2STR(P) converts the polynomial vector P into a string.%For example: P = 234 becomes the string 2s2 + 3s + 4 %MMP2STR(P,V) generates the string using the variable V%instead of s. MMP2STR(234, z ) becomes 2z2 + 3z + 4 %MMP2STR(P,V,1) factors the polynomial into the product of a%constant and a monic polynomial.%MMP2STR(234,1) becomes 2(s2 + 1.5s + 2) %Copyright (c) 1996 by Prentice-Hall,Inc.if nargin3, ff=0; end%factored form is Falseif nargin 2, v= s ; end%default variable is s if isempty(v), v= s ; end%default variable is s v=v(1) ;%variable must be scalar p=mmpsim(p) ;%strip insignificant termsn=length(p) ;if ff%put in factored formK=p(1) ; Ka=abs(K) ; p=p/K;if abs(K-1)1e-4pp=; pe= ;elseif abs(K+1)1e-4pp= -( ; pe= ) ;elseif abs(Ka-round(Ka)=1e-5*Kapp=sprintf( %.0f , K) *( ; pe= ) ;elsepp=sprintf( %.4g , K) *( ; pe= ) ;endelse%not factored formK=p(1);pp=sprintf( %.4g , K) ;pe=;endif n=1%polynomial is just a constants=sprintf( %.4g ,K);returnends=pp v sprintf( %.0f ,n-1);%begin string constructionfor i=2:n-1%catenate center terms in polynomialif p(i)0, pm= - ;else,if p(i)0,pm= ;endif p(i)= =1,pp= ; else,pp=sprintf( %.4g , abs(p(i) ;endif p(i) =0,s=spmppv sprint