[Rd] qt(p,df) discontinuous in p for df in 1.01->1.7 (PR#2991)

jens.lund at nordea.com jens.lund at nordea.com
Tue May 13 14:29:15 MEST 2003

Full_Name: Jens Lund
Version: Version 1.7.0  (2003-04-16)
OS: Win NT 4.0 SP 6
Submission from: (NULL) (

As the T distribution is symmetrical around 0 qt(0.5,df) should return 0 for any

However for df close to 1 it seems to have problems as seen by:

For example:
> qt(0.5,1.01)
[1] -0.2300470

Higher df as df=1.1 (and up to approx df=1.7) seem to have problems as it also
gives discontinuities (the plural form!):

When df is close to 1 it appears as one discontinuity at p=0.5, and as df
increases there are two discountinuities symmetrical around 0.5 and moving away
from 0.5.

Keep up your outstanding work on R ;-)


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