Home > freetb4matlab > polynomial > polyfit.m

polyfit

PURPOSE ^

% Return the coefficients of a polynomial @var{p}(@var{x}) of degree

SYNOPSIS ^

function [p, s, mu] = polyfit (x, y, n)

DESCRIPTION ^

% -*- texinfo -*-
% @deftypefn {Function File} {[@var{p}, @var{s}, @var{mu}] =} polyfit (@var{x}, @var{y}, @var{n})
% Return the coefficients of a polynomial @var{p}(@var{x}) of degree
% @var{n} that minimizes the least-squares-error of the fit.
%
% The polynomial coefficients are returned in a row vector.
%
% The second output is a structure containing the following fields:
%
% @table @samp
% @item R
% Triangular factor R from the QR decomposition.
% @item X
% The Vandermonde matrix used to compute the polynomial coefficients.
% @item df
% The degrees of freedom.
% @item normr
% The norm of the residuals.
% @item yf
% The values of the polynomial for each value of @var{x}.
% @end table
%
% The second output may be used by @code{polyval} to calculate the 
% statistical error limits of the predicted values.
%
% When the third output, @var{mu}, is present the 
% coefficients, @var{p}, are associated with a polynomial in
% @var{xhat} = (@var{x}-@var{mu}(1))/@var{mu}(2).
% Where @var{mu}(1) = mean (@var{x}), and @var{mu}(2) = std (@var{x}).
% This linear transformation of @var{x} improves the numerical
% stability of the fit.
% @seealso{polyval, residue}
% @end deftypefn

CROSS-REFERENCE INFORMATION ^

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