I'm trying to perform a circle fit to some data points from impedance analysis measurements and although I seem to have compiled a workable function the parameter initialisation is returning no parameters. The equation is; y=yc+((r^2-(x-xc)^2))^0.5 with parameters; yc, xc, r. The data points are given by;
I select the data as normal and go to non-linear curve fitting, choose the function, initialise the parameters which seems to do nothing and then press fit, which fails. Help!
OriginPro 9 and 9.1 have Implicit fitting and come with the Circle function built in: f = (x-xc)^2 + (y-yc)^2 - r^2 Without Implicit fitting, functions can only solve for one root, so any Circle function could only include either the positive root ( such as your y = yc + ((r^2-(x-xc)^2))^0.5 ) or the negative root ( y = yc - ((r^2-(x-xc)^2))^0.5 ). Unfortunately, your data is definitely the negative part of a circle so you need to change your function accordingly.
Circle Fit Parameter Initialisation Issue
Posted - 11/14/2013 : 1:53:15 PM
