regfalsi.m

various matlab programs to slove various problems

function [xvect,xdif,fx,nit]=regfalsi(xm1,x0,toll,nmax,fun)
nit=0; 
x=xm1; 
f=eval(fun); 
fx=[f]; 
x=x0; 
f=eval(fun); 
fx=[fx, f]; 
xvect=[xm1,x0]; 
xdif=[]; 
f=toll+1; 
kprime=1;
while (nit < nmax & (abs(f) > toll)
    nit=nit+1; 
    dim=length(xvect); 
    x=xvect(dim); 
    fxk=eval(fun); 
    xk=x; 
    i=dim; 
    while (i >= kprime)
       i=i-1; 
       x=xvect(i); 
       fxkpr=eval(fun);
       if ((fxkpr*fxk) < 0)
         xkpr=x; kprime=i; break; end; 
    end;
    x=xk-fxk*(xk-xkpr)/(fxk-fxkpr); xvect=[xvect, x]; f=eval(fun); 
    fx=[fx, f]; err=abs(x-xkpr); xdif=[xdif, err];
end;