[R] difference between max in summary table and max function

[Franckx Laurent]

Thanks for the clarification. The basic error on my side was that I had misunderstood the "digits" option in the summary, I had not understood that even integer numbers might end up being "rounded". Problem is solved now.

-----Original Message-----
From: Allen Bingham [mailto:aebingham2 at gmail.com]
Sent: zaterdag 14 februari 2015 8:16
To: 'Martyn Byng'; r-help at r-project.org
Cc: Franckx Laurent
Subject: RE: [R] difference between max in summary table and max function

I thought I'd chime in ... submitting the following:

   ?summary

Provides the following documentation for the default for generalized argument (other than class="data.frame", "factor", or "matrix"):

   ## Default S3 method:
   summary(object, ..., digits = max(3, getOption("digits")-3))

so passing along the object "testrow" w/o a corresponding argument for digits ... defaults to digits=4 (assuming your system has the same default option of digits = 7 that mine does).

... and since later in the documentation it indicates that digits is an:

   integer, used for number formatting with signif()

so noting that all of the values you reported from summary(testrow) all have
4 significant digits (including the Max. of 131500) (excepting the min value of "1"), summary() is doing what it is documented to do.

... sorry for being pedantic --- but doing so to point out how helpful the "?" command can be sometimes.

Hope this helps.

______________________________________
Allen Bingham
Bingham Statistical Consulting
aebingham2 at gmail.com
LinkedIn Profile: www.linkedin.com/pub/allen-bingham/3b/556/325





-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Martyn Byng
Sent: Friday, February 13, 2015 3:15 AM
To: Franckx Laurent; r-help at r-project.org
Subject: Re: [R] difference between max in summary table and max function

Its a formatting thing, try

summary(testrow,digits=20)

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Franckx Laurent
Sent: 13 February 2015 11:00
To: r-help at r-project.org
Subject: [R] difference between max in summary table and max function

Dear all

I have found out that the max in the summary of an integer vector is not always equal to the actual maximum of that vector. For example:


> testrow <- c(1:131509)
> summary(testrow)
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.
      1   32880   65760   65760   98630  131500
> max(testrow)
[1] 131509

This has occurred both in a Windows and in a Linux environment.

Does this mean that the max value in the summary is only an approximation?

Best regards

Laurent Franckx, PhD
Senior researcher sustainable mobility
VITO NV | Boeretang 200 | 2400 Mol
Tel. ++ 32 14 33 58 22| mob. +32 479 25 59 07 | Skype: laurent.franckx | laurent.franckx at vito.be | Twitter @LaurentFranckx




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