[R] Extracting part of a factor

[Hervé Pagès]

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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>>> 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