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# best practices for web scraping in R // ldply
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# best practices for web scraping in R # | |
# function should be used with ldply | |
# eg: | |
ldply(urls, scrape) | |
# add a try to ignore broken links/ unresponsive pages | |
# eg: | |
ldply(urls, function(url){ | |
out = try(scrape(url)) | |
if(class(out)=='try-error') next; | |
return(out) | |
}) | |
# insert some random sleep interval to prevent getting booted | |
# eg: | |
ldply(urls, function(url){ | |
out = try(scrape(url)) | |
if(class(out)=='try-error') next; | |
Sys.sleep(sample(seq(1, 3, by=0.001), 1)) | |
return(out) | |
}) | |
scrape <- function(url) | |
{ | |
if(!require('XML')){ | |
install.packages('XML') | |
library('XML') | |
} | |
if(!require('RCurl')){ | |
install.packages('RCurl') | |
library('RCurl') | |
} | |
if(!require('plyr')){ | |
install.packages('plyr') | |
library('plyr') | |
} | |
if(!require('stringr')){ | |
install.packages('stringr') | |
library('stringr') | |
} | |
df = data.frame(url=url, stringsAsFactors=F) | |
#download page, use "readLines" if "getURL" fails | |
html = try(getURL(df$url)) | |
if(class(html)=='try-error'){ | |
html = readLines(df$url, warn=F) | |
} | |
tree = htmlTreeParse(html, useInternalNodes=T) | |
#@@@@@@@@@@@@@@@@@@@@# | |
| | | |
| ENTER XPATH HERE: | | |
| | | |
#$$$$$$$$$$$$$$$$$$$$# | |
return(data.frame(df, stringsAsFactors=F)) | |
} |
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Remove curly end brackets on line 59 & 60 e.g. when input specific xpath for your page set.