"Dante Ian Detera" wrote in message <firstname.lastname@example.org>... > I am trying to curve fit a set of data (in x-y plot/form) into an equation using curve fitting tool in mat lab. > > The custom equation is: > y=a*(1-erf(x/(2*sqrt(b*(7.88e+08))))) > > Starting point of a is 1 > Starting point of b is 1e-08 > > I awlays get an error saying: > Fit could not be computed due to error: > > Error in fittype expression ==> a.*(1-erf(x./(2.*sqrt(b.*(7.88e+08))))) > ??? Input must be real. > > I have no idea how to debug this one. Help please. > > Thanks, > Dante
Does the error disappear if you choose the custom equation as y=a*(1-erf(x/(2*sqrt(b^2*(7.88e+08))))) ?