[R] Re: [ -R] Summary converting among modes

[Martin Henry H. Stevens]

Thank you very much for the response.
The way to get rid of those pesky characters is to first convert to
character (from the default factor), THEN convert to numeric. I had tried
using as.is= in read.table, but I used it incorrectly (as.is=TRUE instead of
as.is= <vector of col indices>).

as.numeric( as.character( vect.dat ) )
NOT simply    as.numeric(vect.dat)

I used as.is= incorrectly. I simply used as.is=TRUE, and did not specify
----- Original Message -----
From: "Thomas Lumley" <tlumley at u.washington.edu>
To: "Martin Henry H. Stevens" <hstevens at muohio.edu>
Cc: <r-help at stat.math.ethz.ch>
Sent: Friday, July 27, 2001 1:47 PM
Subject: Re: [R] converting among modes


> On Fri, 27 Jul 2001, Martin Henry H. Stevens wrote:
>
> > Windows 2000, R 1.3.0
> >
> > I have been given a data set (ASCII tab delimited) in which many
variables
> > that are supposed to be numeric actually contain characters. I would be
> > happy to have those character entries disappear and become NA.
> >
> > When I use read.table and then attempt to convert these using
as.numeric(),
> > of course it doesn't work, and I get the ASCII? representation? maybe?
When
> > I use scan() and specify the data type (what=...), I get an error
message
> > saying that I have character data in the numeric variable.
>
> If there are only a few different character strings causing problems you
> can use the na.strings option of read.table().
>
> Your data are actually read as *factors*, not as characters, and
> as.numeric() gives the factor codes.  Converting factors to numeric is a
> FAQ (7.13); use as.numeric(as.character(the.factor))
>
>
> -thomas
>
> Thomas Lumley Asst. Professor, Biostatistics
> tlumley at u.washington.edu University of Washington, Seattle
>
>

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