我想应用一个循环来从 R 中的多个网页中抓取数据。我能够抓取一个网页的数据,但是当我尝试对多个页面使用循环时,我收到了一个令人沮丧的错误。我花了几个小时修修补补,但无济于事。任何帮助将不胜感激!!!
这有效:
###########################
# GET COUNTRY DATA
###########################
library("rvest")
site <- paste("http://www.countryreports.org/country/","Norway",".htm", sep="")
site <- html(site)
stats<-
data.frame(names =site %>% html_nodes(xpath="//*/td[1]") %>% html_text() ,
facts =site %>% html_nodes(xpath="//*/td[2]") %>% html_text() ,
stringsAsFactors=FALSE)
stats$country <- "Norway"
stats$names <- gsub('[\r\n\t]', '', stats$names)
stats$facts <- gsub('[\r\n\t]', '', stats$facts)
View(stats)
但是,当我尝试在循环中编写此内容时,我收到错误
###########################
# ATTEMPT IN A LOOP
###########################
country<-c("Norway","Sweden","Finland","France","Greece","Italy","Spain")
for(i in country){
site <- paste("http://www.countryreports.org/country/",country,".htm", sep="")
site <- html(site)
stats<-
data.frame(names =site %>% html_nodes(xpath="//*/td[1]") %>% html_text() ,
facts =site %>% html_nodes(xpath="//*/td[2]") %>% html_text() ,
stringsAsFactors=FALSE)
stats$country <- country
stats$names <- gsub('[\r\n\t]', '', stats$names)
stats$facts <- gsub('[\r\n\t]', '', stats$facts)
stats<-rbind(stats,stats)
stats<-stats[!duplicated(stats),]
}
Error:
Error: length(url) == 1 is not TRUE
In addition: Warning message:
In if (grepl("^http", x)) { :
the condition has length > 1 and only the first element will be used