I have a simple problem in python and matplotlib.

I have 3 lists : x, y and rho with rho[i] a density at the point x[i], y[i].

All values of x and y are between -1. and 1. but they are not in a specific order.

How to make a contour plot (like with imshow) of the density rho (interpolated at the points x, y).

Thank you very much.

EDIT : I work with large arrays : x, y and rho have between 10,000 and 1,000,000 elements

## Best Solution

You need to interpolate your

`rho`

values. There's no one way to do this, and the "best" method depends entirely on the a-priori information you should be incorporating into the interpolation.Before I go into a rant on "black-box" interpolation methods, though, a radial basis function (e.g. a "thin-plate-spline" is a particular type of radial basis function) is often a good choice. If you have millions of points, this implementation will be inefficient, but as a starting point: