cls

dim x(50)
dim y(50)

print
print "Lagrangian Interpolation"
print
input "Number of points to input? "; p

for i=1 to p
    cls
    print
    print "x of point ";i;
    input " = "; x1
    print "y of point ";i;
    input " = "; y1
    x(i)=x1
    y(i)=y1
next i

[again]

cls
print
print "Interpolate: x= ";
input " "; a

b=0
for j=1 to p
    t=1
    for i=1 to p
        if i<>j then t=t*(a-x(i))/(x(j)-x(i))
    next i
    b=b+t*y(j)
next j
print "             y=   ";b
print
print "Another point? (y/n)";
input " ";c$
if c$="y" goto [again]
cls
end