NM expirement. Author: Pousqie

Lagrange.wxm

/* [wxMaxima batch file version 1] [ DO NOT EDIT BY HAND! ]*/
/* [ Created with wxMaxima version 11.08.0 ] */

/* [wxMaxima: input   start ] */
load(draw)$
Lagrange(x, fn, X, N) :=
    sum(
        fn(X[i]) * product(
            if equal(i, j) 
                then 1
            else
                (x - X[j]) / (X[i] - X[j]),
        j, 1, N),
    i, 1, N);
/* [wxMaxima: input   end   ] */

/* [wxMaxima: input   start ] */
L:[1, 25, 12, 8, 3, 2.17, 23, 22.4, 19, 24, 0, 13, 23.9, 7, 10.88888]$
J[0](x) := sin(x)$
J[1](x) := abs(x-12)/10$

fnum : 0$
xmin: 0$
xmax: 25$
f(x, N) := Lagrange(x, J[fnum], L, N)$
/* [wxMaxima: input   end   ] */

/* [wxMaxima: input   start ] */
for k:1 thru length(L) do
    draw2d(
        terminal   = png,
        file_name  = concat("mxga", if k < 10 then concat(0,k) else k),
        dimensions = [600, 200],
        yrange = [-1, 1],
        color = blue,
        explicit(f(x, k), x, xmin, xmax),
        color = red,
        explicit(J[fnum](x), x, xmin, xmax)
    );
system("convert -delay 100 mxga*.png plot.gif && rm mxga*")$
/* [wxMaxima: input   end   ] */

/* [wxMaxima: input   start ] */
wxplot2d([J[fnum](x), f(x, length(L))], [x,xmin,xmax])$
/* [wxMaxima: input   end   ] */

/* Maxima can't load/batch files which end with a comment! */
"Created with wxMaxima"$