[R] is.numeric

[Frank E Harrell Jr]

On Thu, 20 Feb 2003 10:58:46 +0100
Arne Henningsen <ahenningsen at email.uni-kiel.de> wrote:

> Hi,
> I have a vector, which contains both strings and numbers, e.g.
> 
> > foo <- c("str1",1234,"str2",0.9876)
> 
> I want to know if a distinct element of the vector is a string or a number and 
> took "is.numeric", but
> 
> > is.numeric(foo[2])
> [1] FALSE
> 
> because R treats the numbers in a mixed vectors as strings:
> 
> > foo
> [1] "str1"   "1234"   "str2"   "0.9876"
> 
> As a workaround I use:
> 
> > !is.na(as.numeric(foo[2]))
> [1] TRUE
> > !is.na(as.numeric(foo[1]))
> [1] FALSE
> Warning message:
> NAs introduced by coercion
> 
> This works, but I always get the spurious warning messages. Do you know a 
> better way or a way to suppress these warning messages?
> 
> Thanks,
> Arne
> 
> -- 
> Arne Henningsen
> Department of Agricultural Economics
> Christian-Albrechts-University Kiel
> 24098 Kiel, Germany
> Tel: +49-431-880-4445
> Fax: +49-431-880-1397 
> ahenningsen at email.uni-kiel.de
> http://www.uni-kiel.de/agrarpol/ahenningsen.html
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
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This function in the Hmisc library may help:

all.is.numeric <- function(x, what=c('test','vector')) {
  what <- match.arg(what)
  old <- options(warn=-1)
  on.exit(options(old))
  xs <- x[x!='' & x!=' ']
  isnum <- !any(is.na(as.numeric(xs)))
  if(what=='test') isnum else if(isnum) as.numeric(x) else x
}


-- 
Frank E Harrell Jr              Prof. of Biostatistics & Statistics
Div. of Biostatistics & Epidem. Dept. of Health Evaluation Sciences
U. Virginia School of Medicine  http://hesweb1.med.virginia.edu/biostat