###

Matlab listing: `qint.m`

function [p,y,a] = qint(ym1,y0,yp1) %QINT Quadratic interpolation of 3 uniformly spaced samples % % [p,y,a] = qint(ym1,y0,yp1) % % returns extremum-location p, height y, and half-curvature a % of a parabolic fit through three points. % The parabola is given by y(x) = a*(x-p)^2+b, % where y(-1)=ym1, y(0)=y0, y(1)=yp1. p = (yp1 - ym1)/(2*(2*y0 - yp1 - ym1)); if nargout>1 y = y0 - 0.25*(ym1-yp1)*p; end; if nargout>2 a = 0.5*(ym1 - 2*y0 + yp1); end;

**Next Section:**

Matlab listing: zpfmin.m

**Previous Section:**

Matlab listing: maxr.m