[R] qt with ncp?

[Peter Dalgaard BSA]

Peter Malewski <peter.malewski at gmx.de> writes:

> Does anybody has a function or idea how to calculate qt with a noncentrality 
> parameter? I'm porting a SAS-macro for equivalence (Wellek, 1994 TT2ST) to R 
> and it seems that I need this to calculate tinv (SAS-command, I hope that 
> this is R's qt,...I get the SAS-macro manual next week).

The easiest way is probably to use something like

uniroot(function(x)pt(x, df, ncp) - p, c(-1e7,1e7))

It's not going to be fast, but if you just need one of them...

(Look inside power.t.test for variations on the theme)

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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