From ripley@stats.ox.ac.uk  Wed Jul 25 20:41:34 2001
From: ripley@stats.ox.ac.uk (Prof Brian Ripley)
Date: Wed, 25 Jul 2001 20:41:34 +0100 (BST)
Subject: [Rd] bug in pretty() (PR#1032)
In-Reply-To: <200107251706.TAA06210@pubhealth.ku.dk>
Message-ID: <Pine.LNX.4.31.0107252038150.2501-100000@gannet.stats>

On Wed, 25 Jul 2001 deepayan@stat.wisc.edu wrote:

>
>
>
> I have the following output from pretty():
>
>
> > pretty(c(-.1, 1)) # note 2nd element
> [1] -2.000000e-01 -2.775558e-17  2.000000e-01  4.000000e-01  6.000000e-01
> [6]  8.000000e-01  1.000000e+00
> > as.character(pretty(c(-.1, 1)))
> [1] "-0.2"                  "-2.77555756156289e-17" "0.2"
> [4] "0.4"                   "0.6"                   "0.8"
> [7] "1"
>
>
> The root cause seems to be here:
>
>
> > 1.2/6 - .2
> [1] -2.775558e-17

You can't expect exact arithmetic.  Using as.character is almost never a
good idea.  I don't think this is a bug, but you should be doing something
more complex if you want to make labels here.

> (It seems that this is not a problem in all installations.)
>
>
> <<insert bug report here>>

!!
>
> --please do not edit the information below--
>
> Version:
>  platform = i686-pc-linux-gnu
>  arch = i686
>  os = linux-gnu
>  system = i686, linux-gnu
>  status =
>  major = 1
>  minor = 3.0
>  year = 2001
>  month = 06
>  day = 22
>  language = R
>
> Search Path:
>  .GlobalEnv, package:ctest, Autoloads, package:base
>
>
>
>
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-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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[Rd] bug in pretty() (PR#1032)
Prof Brian Ripley