[R] extracting character values

[Uwe Ligges]

On 13.01.2013 18:02, Biau David wrote:
> OK,
>
> here is a minimal working example:
>
> au1 <- c('biau dj', 'jones kb', 'van den hoofs j', ' biau dj', 'biau dj', 'campagna r', 'biau dj', 'weiss kr', 'verdegaal sh', 'riad s')
> au2 <- c('weiss kr', 'ferguson pc', ' greidanus nv', ' porcher r', 'ferguson pc', 'pessis e', 'leclerc p', 'biau dj', 'bovee jv', 'biau d')
> au3 <- c('bhumbra rs', 'lam b', 'garbuz ds', NA, 'chung p', ' biau dj', 'marmor s', 'bhumbra r', 'pansuriya tc', NA)
>
> netw <- data.frame(au1, au2, au3)
> res <- data.frame(matrix(NA, nrow=dim(netw)[1], ncol=dim(netw)[2]))
>
> for (i in 1:dim(netw)[2])
> {
> wh <- regexpr('[a-z]{3,}', as.character(netw[,i]))
> res[i] <- substring(as.character(netw[,i]), wh, wh + attr(wh,'match.length')-1)
> }


There may be an easier solution, but this should do:

res <- data.frame(lapply(netw,
      function(x)
        gsub("^ *([[:alpha:] ]*) +[[:alpha:]]+$", "\\1", x)))

Uwe Ligges




>   problem is for author "van den hoofs j" who is only retrieved as 'van'
>
> thanks,
>
>
> David Biau
>
>
>> ________________________________
>> De : arun <smartpink111 at yahoo.com>
>> À : Biau David <djmbiau at yahoo.fr>
>> Envoyé le : Dimanche 13 janvier 2013 17h38
>> Objet : Re: [R] extracting character values
>>
>> HI,
>>
>>
>>   res <- data.frame(matrix(NA, nrow=dim(netw)[1], ncol=dim(netw)[2]))
>> #Error in matrix(NA, nrow = dim(netw)[1], ncol = dim(netw)[2]) :
>>   # object 'netw' not found
>> Can you provide an example dataset of netw?
>> Thanks.
>> A.K.
>>
>>
>>
>> ----- Original Message -----
>> From: Biau David <djmbiau at yahoo.fr>
>> To: r help list <r-help at r-project.org>
>> Cc:
>> Sent: Sunday, January 13, 2013 3:53 AM
>> Subject: [R] extracting character values
>>
>> Dear all,
>>
>> I have a dataframe of names (netw), with each cell including last name and initials of an author; some cells have NA. I would like to extract only the last name from each cell; this new dataframe is calle 'res'
>>
>>
>> Here is what I do:
>>
>> res <- data.frame(matrix(NA, nrow=dim(netw)[1], ncol=dim(netw)[2]))
>>
>> for (i in 1:x)
>> {
>> wh <- regexpr('[a-z]{3,}', as.character(netw[,i]))
>> res[i] <- substring(as.character(netw[,i]), wh, wh + attr(wh,'match.length')-1)
>> }
>>
>>
>> the problem is that I cannot manage to extract 'complex' names properly such as ' van der hoops bf  ': here I only get 'van', the real last name is 'van der hoops' and 'bf' are the initials. Basically the last name has always a minimum of 3 consecutive letters, but may have 3 or more letters separated by one or more space; the cell may start by a space too; initials never have more than 2 letters.
>>
>> Someone would have a nice idea for that? Thanks,
>>
>>
>> David
>>
>>      [[alternative HTML version deleted]]
>>
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>>
>>
> 	[[alternative HTML version deleted]]
>
>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>