From maechler at stat.math.ethz.ch  Wed Jul 25 09:57:26 2007
From: maechler at stat.math.ethz.ch (maechler at stat.math.ethz.ch)
Date: Wed, 25 Jul 2007 09:57:26 +0200 (CEST)
Subject: [Rd] Accuracy of qt for df=1 (PR#9804)
Message-ID: <20070725075726.1FE12667E6@slim.kubism.ku.dk>

>>>>> "MW" == Morten Welinder <mwelinder at gmail.com>
>>>>>     on Tue, 24 Jul 2007 17:18:09 +0200 (CEST) writes:

    MW> Full_Name: Morten Welinder
    MW> Version: 2.2.0
    MW> OS: Linux
    MW> Submission from: (NULL) (216.223.241.229)


    MW> The qt function for df=1 is implemented as...

    MW> q = - tan((P+1) * M_PI_2);

    MW> Adding 1 kills accuracy for P near 0.  A better way is to use

    MW> q = cot(P * M_PI_2);
    MW> or
    MW> q = 1/tan(P * M_PI_2);


Yes, indeed, thanks a lot, Morten!!

     ((BTW: you should really upgrade your version of R))

Best regards,
Martin



[Rd] Accuracy of qt for df=1 (PR#9804)
maechler at stat.math.ethz.ch