Help: Plotting points through a 39gii Program



#4

I am attempting a plot where:

x axis: x_1

and y axis: f(x_1)

where x_k is determined by:

x_1 = x_0 - f(x_0)/f'(x_0) (Newton's Method)

So far my program is:

NEWTPATH(t,n)

BEGIN

LOCAL k,w,y;

RECT();

FOR k FROM 1 TO n DO

t-(F1(t)/der(F1(X),X=t))- > w;

F1(w)- > y;

PIXON(w,y);

w- > t;

END;

FREEZE;

END;

The "der" is the derivative funtion.

The program either freezes at the input screen or gives me an "out of bounds" error. I have F1(X) already stored before running the program. Any ideas? Thanks!

Eddie

Edited: 4 Nov 2012, 11:43 a.m.


#5

Have you checked that the derivative is never going null? Just my 2 cents...


#6

I am not sure. When I tried debugging the program the calcualtor goes into "space" when it approaches the loop.

Apparently, der(F1(X),X=t) isn't allowed in a program. I think this is what you meant by the derivative being null. Really dumb not to allow calculus functions.

This is what I have now:

NEWTPATH(g,n)

BEGIN

LOCAL k,w,y,h,d,X;

RECT();

FOR k FROM 1 TO n DO

F1(g)->h;

der(F1(X),X=g)->d;

t-h/d->w;

F1(w)->y;

PRINT(w);

w->t;

END;

END;


Now I get a syntax error on Line 8 every time. Even if I change the der(F1(X),X=g)->d to 1->d, I still get this error. I have no idea where I have the syntax error, I localized all the varaibles, including X.

Edited: 4 Nov 2012, 1:56 p.m.


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