[R] read.table and missing values

Prof Brian Ripley ripley at stats.ox.ac.uk
Tue Jun 19 16:23:53 CEST 2001

On Tue, 19 Jun 2001, Peter Breuer wrote:

> I'd like to share data files (tab delimited text files)
> that i read in via read.table with other applications.
> Missing data are empty fields (two tabs following each other)
> I couldn't find a way yet to 'convince' R to interprete this to be
> missing values.

It's the default ....

> The read.table option na.strings="" or na.strings='' didn't work.
> using any special character in the data file for missings (like '#')
> and defining it for missing using na.strings="#" worked.
> So I was able to solve the problem doing a global replace.
> But I'd prefer to read in the data files as is and wonder whether
> there is a possibility to that in R.
> Data Import/Export Manual says that empty fields in numeric columns
> are regarded as missing values.
> But with my versions of R (Windows 1.2.3, Mac) it didn't work
> Documention, FAQ and the mailing archive didn't have any further hint.
> Thanks for any advice

It works as documented, and as documented does what you want (so no
further hint is needed).  For file foo.dat


I get

> read.table("foo.dat", header=T, sep=",")
   a  b c
1  1  2 3
2  4 NA 6
3 NA  8 9

as advertised.

You have set sep="\t", haven't you?  The default separator is white space,
and that will swallow two tabs.  The following had tabs in originally,

a	b	c
1	2	3
4		6
	8	9

and gives

> read.table("foo.dat", header=T, sep="\t")
   a  b c
1  1  2 3
2  4 NA 6
3 NA  8 9

So, if you do that it should work for you too.  And if you want to claim
on R-help that things do not work, please include an example so we can see
what you are doing (or not doing).

Brian D. Ripley,                  ripley at 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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