function T4=taylor(df,a,b,ya,M)%Input   - df=[y' y'' y''' y'''']entered as a string 'df'%          where y'=f(t,y)%        - a and b are the left and right endpoints%        - ya is the initial condition y(a)%        - M is the number of steps%Output  - T4=[T' Y'] where T is the vector of abscissas and%          Y is the vector of ordinates%  NUMERICAL METHODS: Matlab Programs% (c) 2004 by John H. Mathews and Kurtis D. Fink%  Complementary Software to accompany the textbook:%  NUMERICAL METHODS: Using Matlab, Fourth Edition%  ISBN: 0-13-065248-2%  Prentice-Hall Pub. Inc.%  One Lake Street%  Upper Saddle River, NJ 07458h=(b-a)/M;T=zeros(1,M+1);Y=zeros(1,M+1);T=a:h:b;Y(1)=ya;for j=1:M   D=feval(df,T(j),Y(j));   Y(j+1)=Y(j)+h*(D(1)+h*(D(2)/2+h*(D(3)/6+h*D(4)/24)));endT4=[T' Y'];