From Graeme.Ambler at bristol.ac.uk  Mon Sep  8 15:57:48 2003
From: Graeme.Ambler at bristol.ac.uk (Graeme.Ambler@bristol.ac.uk)
Date: Mon Sep  8 14:57:15 2003
Subject: [Rd] Accuracy problems in summary()? (PR#4101)
Message-ID: <200309081257.h88CvmJH013213@pubhealth.ku.dk>

Full_Name: Graeme Ambler
Version: 1.7.1
OS: Red Hat Linux 9
Submission from: (NULL) (137.222.80.161)


There seems to be a curious accuracy-related problem in summary().  Try the
following:

test<-matrix(rnorm(2000),nc=2)
summary(test)
summary(test[,1])

The first use of summary() is fine.  The second will lie to you about the
accuracy to which numbers are displayed.  The results I got were:

> summary(test)
       X1                 X2
 Min.   :-2.68358   Min.   :-3.780882
 1st Qu.:-0.67451   1st Qu.:-0.721148
 Median : 0.01577   Median : 0.006311
 Mean   : 0.00644   Mean   :-0.022287
 3rd Qu.: 0.69642   3rd Qu.: 0.630215
 Max.   : 3.11174   Max.   : 2.827698
> summary(test[,1])
    Min.  1st Qu.   Median     Mean  3rd Qu.     Max.
-2.68400 -0.67450  0.01577  0.00644  0.69640  3.11200

Accuracy in the second case always seems to be 4SF, yet 6 are displayed in some
cases.  I have been able to reproduce this bug with 100% reliability.  Apologies
if this has been reported before, I couldn't find it when I searched.


[Rd] Accuracy problems in summary()? (PR#4101)
Graeme.Ambler@bristol.ac.uk