javascript: Polynomial regression

regression.js is a javascript library containing a collection of least squares fitting methods for finding a trend in a set of data. It currently contains methods for linear, exponential, logarithmic, power and polynomial trends


it even has nice charting by using flot.js


Polynomial Regression Data Fit (polysolve, js)
another online tool, with charting


Polynomial interpolation - Wikipedia, the free encyclopedia:

The red dots denote the data points (xk,yk),
while the blue curve shows the interpolation polynomial.