FindFit for the 4-parameter beta distribution

[Anna Kaladze]

Hi all,

I am trying to use FindFit in order to choose p and q parameters of ft function (which is actually a 4-parameter beta distribution) to match "data". I do not know why I get the Jacobean not being real warning at all times and also very poor fits. (If I do not specify starting guesses I get p->1 and q->1). Even if I specify starting values for p and q, FindFit just returns those very values. Can you please help me to have this curve fitting work properly? Maybe I am doing something wrong. The code is attached.

Thanks a lot.

Anna.

 

[NateD]

dat = {0.16, 0.067, 0.14, 0.093, 0.067, 0.087, 0.134, 0.067, 0.133, 0.12};ft[x_, p_, q_] := Beta[x, p, q]/(Beta[1, p, q]);sol = FindFit[dat, ft[x, p, q], {p, q}, x]Plot[ft[x, p, q] /. sol, {x, 0, 1}, PlotStyle -> Red]Show[ListPlot[dat, PlotStyle -> Blue], Plot[ft[x, p, q] /. sol, {x, 0, 1}, PlotStyle -> Red]]