Pandas Interpolation Method 'Cubic' - spline or polynomial?
In interpolation methods, 'polynomial' generally means that you generate a polynomial with the same number of coefficients as you have data points. So, for 10 data points you would get an order 9 polynomial.
'cubic' generally means piecewise 3rd order polynomials. A sliding window of 4 data points is used to generate these cubic polynomials.
I am trying to understand interpolation in pandas and I  don't seem to understand if the method 'cubic' is a polynomial  interpolation  of  order 3 or a spline. Does anybody know  what  pandas uses behind that method?