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)
}

 problem is for author "van den hoofs j" who is only retrieved as 'van'

thanks,


David Biau


>________________________________
> De : arun <smartpink111@yahoo.com>
>À : Biau David <djmbiau@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@yahoo.fr>
>To: r help list <r-help@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
>
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>
>
>______________________________________________
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>
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>
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