matlab多项式7M文件举例.docVIP

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 data n = 0.000010.000020.0000 ? b%earlier data b = -20-140-320-260 ? mmpsim(n)%strip away negligible leading term ans = 10.000020.0000 ? mmp2str(b)%convert polynomial to string ans = -20s^3 - 140s^2 - 320s^1 - 260 ? mmp2str(b , x ) ans = -20x^3 - 140x^2 - 320x^1 - 260 ? mmp2str(b , [] , 1) ans = -20*(s^3 + 7s^2 + 16s^1 + 13) ? mmp2str(b , x , 1) ans = -20*(x^3 + 7x^2 + 16x^1 + 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; end x=x(:). ;%make sure input is a row i=find(abs(x).99abs(x)tol) ;%find insignificant indices x(i)=zeros(1, length(i)) ;%set them to zero i=find(x~=0) ;%find significant indices if isempty(i) y=0 ;%extreme case: nothing left! else y=x(i(1) : length(x)) ;%start with first term end%and go to end of polynomial function 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 2s^2 + 3s + 4 % %MMP2STR(P,V) generates the string using the variable V %instead of s. MMP2STR([234], z ) becomes 2z^2 + 3z + 4 % %MMP2STR(P,V,1) factors the polynomial into the product of a %constant and a monic polynomial. %MMP2STR([234],[],1) becomes 2(s^2 + 1.5s + 2) %Copyright (c) 1996 by Prentice-Hall,Inc. if nargin3, ff=0; end%factored form is False if 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 terms n=