Hi, I am trying to fit sample data to a Johnson SU distribution in S-Plus. It seems not many people use S-Plus, so if you are familiar with R then you could help as well.(adsbygoogle = window.adsbygoogle || []).push({});

The code that I have is:

f.Jsu.fun.takeslist(x,g,l,r,e)

which is a function I have made that calculates the PDF of each value of the list x and has parameters g,l,r,e corresponding to the Johnson SU distribution. I know this PDF works because I have used it to plot graphs.

fitdistr(turn$all.turn.y.obs,f.Jsu.fun.takeslist,list(g=0.5,r=3,l=3000,e=-200))

is then what I am trying to use to fit the Johnson SU distribution. fitdistr is a native S-Plus function.

Now, the fitdistr doesn't work on this function.

What I have done previously though is fitted the Gumbel distribution using the same approach by creating my own PDF function, and fitdistr worked and provided a good fit.

The Gumbel distribution is 2 parameter and the Johnson SU is 4 parameter, so I am thinking it is just too many parameters for it to handle, although no limits are specified for fitdistr. I am by no means a master of S-Plus or R so I would appreciate anything you guys have to say on this.

Thanks!

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# Fitting 4 parameter distributions in S-Plus (or R)

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