[R] extracting character values

[arun]

HI,

Not sure this helps:
netw<-read.table(text="
lastname_initial, year
Aaron H, 1900
Beecher HW, 1947
Cannon JP, 1985
Stone WC, 1982
 van der hoops bf, 1948
NA, 1976
",sep=",",header=TRUE,stringsAsFactors=FALSE)


res1<-sub("^[[:space:]]*(.*?)[[:space:]]*$","\\1",gsub("\\w+$","",netw[,1]))
res1[!is.na(res1)]
#[1] "Aaron"         "Beecher"       "Cannon"        "Stone"        
#[5] "van der hoops"
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

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