我创建了一个循环函数,它使用具有特定时间间隔的搜索API(可以说每隔5分钟)提取推文。此函数执行它假设的操作:连接到Twitter,提取包含特定关键字的推文,并将它们保存在csv文件中。但是偶尔(每天2-3次)循环停止,因为这两个错误之一:循环函数中的循环错误(用于从Twitter中提取数据)
错误htmlTreeParse(URL,useInternal = TRUE): 错误创建解析器http://search.twitter.com/search.atom?q= 6.95322e -310tst & RPP = 100 &页= 10
错误UseMethod( “xmlNamespaceDefinitions”): 施加到 类 “NULL” 的对象关于 'xmlNamespaceDefinitions' 不适用方法
我希望你能帮助我处理这些错误,回答我的一些问题:
- 是什么原因导致出现这些错误?
- 如何调整我的代码以避免这些错误?
- 我该如何强制循环在遇到错误时继续运行(例如使用Try函数)?
我的功能(基于网上找到几个脚本)如下:
library(XML) # htmlTreeParse
twitter.search <- "Keyword"
QUERY <- URLencode(twitter.search)
# Set time loop (in seconds)
d_time = 300
number_of_times = 3000
for(i in 1:number_of_times){
tweets <- NULL
tweet.count <- 0
page <- 1
read.more <- TRUE
while (read.more)
{
# construct Twitter search URL
URL <- paste('http://search.twitter.com/search.atom?q=',QUERY,'&rpp=100&page=', page, sep='')
# fetch remote URL and parse
XML <- htmlTreeParse(URL, useInternal=TRUE, error = function(...){})
# Extract list of "entry" nodes
entry <- getNodeSet(XML, "//entry")
read.more <- (length(entry) > 0)
if (read.more)
{
for (i in 1:length(entry))
{
subdoc <- xmlDoc(entry[[i]]) # put entry in separate object to manipulate
published <- unlist(xpathApply(subdoc, "//published", xmlValue))
published <- gsub("Z"," ", gsub("T"," ",published))
# Convert from GMT to central time
time.gmt <- as.POSIXct(published,"GMT")
local.time <- format(time.gmt, tz="Europe/Amsterdam")
title <- unlist(xpathApply(subdoc, "//title", xmlValue))
author <- unlist(xpathApply(subdoc, "//author/name", xmlValue))
tweet <- paste(local.time, " @", author, ": ", title, sep="")
entry.frame <- data.frame(tweet, author, local.time, stringsAsFactors=FALSE)
tweet.count <- tweet.count + 1
rownames(entry.frame) <- tweet.count
tweets <- rbind(tweets, entry.frame)
}
page <- page + 1
read.more <- (page <= 15) # Seems to be 15 page limit
}
}
names(tweets)
# top 15 tweeters
#sort(table(tweets$author),decreasing=TRUE)[1:15]
write.table(tweets, file=paste("Twitts - ", format(Sys.time(), "%a %b %d %H_%M_%S %Y"), ".csv"), sep = ";")
Sys.sleep(d_time)
} # end if
'tryCatch'和'try'是什么你在追求。 –
关于如何实施tryCatch或尝试的任何建议? – Gert
TryCatch +有用链接的示例: http://stackoverflow.com/a/2622930/473899 现在运行您的代码,但目前为止还没有收到任何错误,所以我们将看看我是否有任何有用的添加。 – Esteis