[R] Extracting part of a factor

[KMNanus]

Let me see if I can ask the question more clearly - I am trying to extract a section of a hyphenated factor. For example, 001-004 is one observation of test$ken, which is a factor, and I want to set up a new factor variable called place that would have 001 as an observation. If I call mutate(place = (as.character (test$ken)), I can extract 001 from  001-004, but but don't know how to subsequently convert that character string back into a factor.


Or can 001 be extracted from a factor as a factor?

Do you know how to execute either of these approaches?

Ken
kmnanus at gmail.com
914-450-0816 (tel)
347-730-4813 (fax)



> On Mar 3, 2016, at 8:33 PM, Hervé Pagès <hpages at fredhutch.org> wrote:
> 
> On 03/03/2016 02:13 PM, KMNanus wrote:
>> When I do that,
> 
> When you do what exactly?
> 
> It's impossible for anyone here to know what you're doing if you
> don't show the code.
> 
>> I get "Error in `$<-.data.frame`(`*tmp*`, "site", value
>> = integer(0)) :
>>   replacement has 0 rows, data has 6”
>> 
>> The data frame has 6 rows.
> 
> You said you had a factor variable, you never mentioned you had a
> data.frame. If the factor variable is part of a data.frame 'df',
> then first extract it with something like df$myvar or df[["myvar"]],
> and then call substr() followed by as.factor() on it.
> 
> H.
> 
>> 
>> Ken
>> kmnanus at gmail.com <mailto:kmnanus at gmail.com>
>> 914-450-0816 (tel)
>> 347-730-4813 (fax)
>> 
>> 
>>> On Mar 3, 2016, at 4:52 PM, Hervé Pagès <hpages at fredhutch.org
>>> <mailto:hpages at fredhutch.org>> wrote:
>>> 
>>> Hi,
>>> 
>>> On 03/03/2016 12:18 PM, KMNanus wrote:
>>>> I have a factor variable that is 6 digits and hyphenated.  For
>>>> example, 001-014.
>>>> 
>>>> I need to extract the first 3 digits to a new variable using mutate
>>>> in dplyr - in this case 001 - but can’t find a function to do it.
>>>> 
>>>> substr will do this for character strings, but I need the variable to
>>>> remain as a factor.
>>> 
>>> What prevents you from calling as.factor() on the result to turn it
>>> back into a factor?
>>> 
>>> H.
>>> 
>>>> 
>>>> Is there an R function  or workaround to do this?
>>>> 
>>>> 
>>>> Ken
>>>> kmnanus at gmail.com <mailto:kmnanus at gmail.com>
>>>> 914-450-0816 (tel)
>>>> 347-730-4813 (fax)
>>>> 
>>>> 
>>>> 
>>>> ______________________________________________
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>>>> PLEASE do read the posting guide
>>>> http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>> 
>>> 
>>> --
>>> Hervé Pagès
>>> 
>>> Program in Computational Biology
>>> Division of Public Health Sciences
>>> Fred Hutchinson Cancer Research Center
>>> 1100 Fairview Ave. N, M1-B514
>>> P.O. Box 19024
>>> Seattle, WA 98109-1024
>>> 
>>> E-mail: hpages at fredhutch.org <mailto:hpages at fredhutch.org>
>>> Phone:  (206) 667-5791
>>> Fax:    (206) 667-1319
>> 
> 
> -- 
> Hervé Pagès
> 
> Program in Computational Biology
> Division of Public Health Sciences
> Fred Hutchinson Cancer Research Center
> 1100 Fairview Ave. N, M1-B514
> P.O. Box 19024
> Seattle, WA 98109-1024
> 
> E-mail: hpages at fredhutch.org
> Phone:  (206) 667-5791
> Fax:    (206) 667-1319