Whoops, it seems I could use some help with regular expressions...
Consider the following two functions, creating a search string, and retrieving the content from the url,
makeURLsearch <- function(key, dates=c(NULL, NULL)){ base.search <- "http://scholar.google.co.uk/scholar?"; key.search <- paste("as_q=", key,"&", sep="")other.search <- "num=10&btnG=Search + Scholar &as_epq=&as_oq=&as_eq=&as_occt=any&as_sauthors=&as_publication=&" dates.search <- paste("as_ylo=", dates[1], "&as_yhi=", dates[2], "&as_allsubj=all&hl=en&lr=", sep="")full.search <- paste(base.search, key.search, other.search, dates.search, sep="")return(full.search) } makeURLsearch("plasmonics") makeURLsearch("photonics", c(1980, NULL)) retrieveNumberPublications <- function(url){ x <- readLines(url) y <- grep('of about',x, value=TRUE)z <- gsub('of about\\s+</b>','\\1',y[1],perl=TRUE) # this does not do what I wanted# the bit to retrieve is the number below # <b>10</b> of about <b>21,900</b> for <b><b>photonics</b> z }retrieveNumberPublications( makeURLsearch("photonics", c(2008, NULL)) )
I can isolate the long string containing the result I want, but not single out the value which lies between " <b>10</b> of about <b>21,900</b> for <b><b>photonics</b> " .
Any regexp guru to help me out? I've never got my head around these, other than trivial cases.
Many thanks, baptiste On 15 Jan 2009, at 09:45, baptiste auguie wrote:
For the record, I thought I'd share two findings: First, the web of science website does seem to have some sort of API, as discussed here: http://scientific.thomson.com/support/faq/webservices/ It does not seem like a trivial thing to set up though. Second, because I could not pass the search term easily in the address, I looked into Google scholar instead, where a typical search looks like: http://scholar.google.co.uk/scholar?as_q=plasmonics&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=any&as_sauthors=&as_publication=&as_ylo=&as_yhi=1960&as_allsubj=all&hl=en&lr= here it is trivial to create such a string with the desired keyword and dates, and retrieve the number of results using readLines(url) and grep. Thanks to Phil Spector for some pointers. Best wishes, baptiste
_____________________________ Baptiste Auguié School of Physics University of Exeter Stocker Road, Exeter, Devon, EX4 4QL, UK Phone: +44 1392 264187 http://newton.ex.ac.uk/research/emag ______________________________________________ R-help@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.
