I'd suggest fit(Polynomial, data) instead of polyfit(data). The generic fit function is defined in StatsBase.
2014-05-08 14:23 GMT+02:00 Hans W Borchers <hwborch...@gmail.com>: > Because I was a (tiny) bit unsatisfied with the Polynomial package, > I wrote my own polynomial functions, like > > - polyval() to be applied to vectors as well as polynomial types > - roots() that uses the Matlab order in constructing the companion > matrix and finding all roots > - horner() that utilizes the Horner scheme to compute the value > and the derivative of the polynomial at the same time > (useful for a specialized version of Newton's algorithm) > - a deflated Horner function to return p(x) = (x - x0)*q(x) when > x is a root of polynomial p > - polyfit() for fitting polynomials to data, etc. > > I think a polyfit() function should in any case be a part of a polynomial > package. (Is such a function contained in any other package?) > > Besides that an implementation of the Muller algorithm for computing zeros > of > polynomials might be helpful. Or the calculation of the number of real > roots > of a polynomial in an interval (Descartes' and Sturm's rules). There is > more > interesting numerical stuff that could be part of such a polynomial > package. > > > On Thursday, May 8, 2014 3:42:03 AM UTC+2, Tony Kelman wrote: >> >> Yes, Polynomial is using a different convention than Matlab or what you >> used below in how it constructs the companion matrix. Polynomials.jl uses >> yet another convention. Both produce more accurate (comparable to Matlab) >> results for the roots of the Wilkinson polynomial if you just switch the >> indices during construction of the companion matrix. See >> https://github.com/vtjnash/Polynomial.jl/blob/ >> master/src/Polynomial.jl#L350-L353 for Polynomial, or https://github.com/ >> loladiro/Polynomials.jl/blob/master/src/Polynomials.jl#L324-L325 for >> Polynomials. >> >> I think the intent (see https://github.com/vtjnash/Polynomial.jl/issues/5) >> is to deprecate Polynomial and switch the coefficient order by developing >> under the Polynomials name going forward, but Keno's probably been too busy >> to register the new package, turn on issues, etc. I'm doing some work on >> piecewise stuff in a branch of Polynomials, I might just adopt the package. >> I know David de Laat has put together packages for sparse multivariate >> polynomials https://github.com/daviddelaat/MultiPoly.jl and orthogonal >> polynomials https://github.com/daviddelaat/Orthopolys.jl, don't think >> they're registered but it might make sense to eventually unify all of these >> into the same package. >> > > -- Med venlig hilsen Andreas Noack Jensen
