secant.m

various matlab programs to slove various problems

function [xvect,xdif,fx,nit]=secant(xm1,x0,nmax,toll,fun)
x=xm1; 
fxm1=eval(fun); 
xvect=[x]; 
fx=[fxm1]; 
x=x0; 
fx0=eval(fun);  
xvect=[xvect;x]; 
fx=[fx;fx0]; 
err=toll+1; 
nit=0; 
xdif=[];
while (nit < nmax & err > toll),
    nit=nit+1; 
    x=x0-fx0*(x0-xm1)/(fx0-fxm1); 
    xvect=[xvect;x]; 
    fnew=eval(fun); 
    fx=[fx;fnew]; 
    err=abs(x0-x); 
    xdif=[xdif;err];
    xm1=x0; 
    fxm1=fx0; 
    x0=x; 
    fx0=fnew;
end
return