[R] string-to-number

[Roger Bivand]

On Sat, 19 Aug 2006, Charles Annis, P.E. wrote:

> Greetings, Amigos:
> 
> I have been trying without success to convert a character string,
> > repeated.measures.columns
> [1] "3,6,10"
> 
> into c(3,6,10) for subsequent use.
> 
> as.numeric(repeated.measures.columns) doesn't work (likely because of the
> commas)
> [1] NA
> Warning message:
> NAs introduced by coercion
> 
> I've tried many things including 
> strsplit(repeated.measures.columns, split = ",")
> 
> which produces a list with only one element, viz:
> [[1]]
> [1] "3"  "6"  "10"
> 
> as.numeric() doesn't like that either.

repeated.measures.columns is a vector. Consider:

repeated.measures.columns <- c("3,6,10", "5,4,9")
lst <- strsplit(repeated.measures.columns, split = ",")
lapply(lst, as.numeric)

which is why strsplit() returns a list - one list component for each 
repeated.measures.columns element. Just pick off the one you want with 
[[]]:

as.numeric(strsplit(repeated.measures.columns, split = ",")[[1]])


> 
> Clearly: 1) I cannot be the first person to attempt this, and 2) I've made
> this WAY harder than it is.
> 
> Would some kind soul please instruct me (and perhaps subsequent searchers)
> how to convert the elements of a string into numbers?
> 
> Thank you.
> 
> 
> Charles Annis, P.E.
> 
> Charles.Annis at StatisticalEngineering.com
> phone: 561-352-9699
> eFax:  614-455-3265
> http://www.StatisticalEngineering.com
>  
> 
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> 

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no