This script generates a cubic polynomial from four points. The x coordinates x_{1} through x_{4} must all be different. The script will also interpolate (or even extrapolate!) to give a y value for any x coordinate, x_{5}. Just for the sake of example, the page automatically loads width the results from the four points (-1,-1), (2,2), (3,1) and (4,2) with an interpolation to x=2.5.

y=2.8+1.8x

-1.7x^{2}+0.3x^{3}

y(x_{5})=1.3625

y=2.8+1.8*x

-1.7*x**2+0.3*x**3