[Numpy-discussion] Polynomial evaluation inconsistencies (original) (raw)
Maxwell Aifer maifer at haverford.edu
Fri Jun 29 22:21:18 EDT 2018
- Previous message (by thread): [Numpy-discussion] Proposal to accept NEP 15: Merging multiarray and umath
- Next message (by thread): [Numpy-discussion] Polynomial evaluation inconsistencies
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
Hi, I noticed some frustrating inconsistencies in the various ways to evaluate polynomials using numpy. Numpy has three ways of evaluating polynomials (that I know of) and each of them has a different syntax:
numpy.polynomial.polynomial.Polynomial <https://docs.scipy.org/doc/numpy-1.13.0/reference/generated/numpy.polynomial.polynomial.Polynomial.html#numpy.polynomial.polynomial.Polynomial>: You define a polynomial by a list of coefficients in order of increasing degree, and then use the class’s call() function.
np.polyval <https://docs.scipy.org/doc/numpy-1.13.0/reference/generated/numpy.polyval.html>: Evaluates a polynomial at a point. First argument is the polynomial, or list of coefficients in order of decreasing degree, and the second argument is the point to evaluate at.
np.polynomial.polynomial.polyval <https://docs.scipy.org/doc/numpy-1.12.0/reference/generated/numpy.polynomial.polynomial.polyval.html>: Also evaluates a polynomial at a point, but has more support for vectorization. First argument is the point to evaluate at, and second argument the list of coefficients in order of increasing degree.
Not only the order of arguments is changed between different methods, but the order of the coefficients is reversed as well, leading to puzzling bugs (in my experience). What could be the reason for this madness? As polyval is a shameless ripoff of Matlab’s function of the same name <https://www.mathworks.com/help/matlab/ref/polyval.html> anyway, why not just use matlab’s syntax (polyval([c0, c1, c2...], x)) across the board? -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/numpy-discussion/attachments/20180629/fad9ba77/attachment.html>
- Previous message (by thread): [Numpy-discussion] Proposal to accept NEP 15: Merging multiarray and umath
- Next message (by thread): [Numpy-discussion] Polynomial evaluation inconsistencies
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]