Question

当我尝试重建网址时，出现问题“ preNode [[1]]中的错误：下标超出范围”。我的代码在下面列出，我通过樱花比赛的跑步者URL提取信息。

请让我知道我的重构是否有问题：/。

Installing XML Package

install.packages("XML")
library(XML)

#Establish the View Page Source of the Web Site 
ubase = "http://www.cherryblossom.org/"
url = paste(ubase, "/results/2012/2012cucb10m-m.htm", sep = "")
doc = htmlParse(url)

preNode = getNodeSet(doc, "//pre")
txt = xmlValue(preNode[[1]])
nchar(txt)

substr(txt, 1, 50)
substr(txt, nchar(txt) - 50, nchar(txt))

els = strsplit(txt, "\\r\\n")[[1]]
length(els)
els[1:3]

els[ length(els) ]

extractResTable =
  # Retrieve data from web site, find preformatted text,
  # return as a character vector.
  function(url)
   {
    doc = htmlParse(url)
    preNode = getNodeSet(doc, "//pre")
    txt = xmlValue(preNode[[1]])
    els = strsplit(txt, "\r\n")[[1]]
    return(els)
  }

# Retrieve the 2012 Men's Results 
m2012 = extractResTable(url)
identical(m2012, els)

#Setting a vector of all the URLS for each year 
ubase = "http://www.cherryblossom.org/"
urls = paste(ubase, "results/", 1999:2012, "/",
             1999:2012, "cucb10m-m.htm", sep = "")

# Apply the extractRestTable() to "urls" 
menTables = lapply(urls, extractResTable)

#Resolving the error message
options(error = recover)
menTables = lapply(urls, extractResTable) #Choose Selection 2

# After choosing Selection 2, enter ls() in the console below
# The list should display: [1] "doc"     "preNode" "url"
# Proceed if so by:
# 1. Enter url in the console. 
  # Output: [1] "http://www.cherryblossom.org/results/1999/1999cucb10m-m.htm"
# 2. Enter length(preNode)
  # Output: [1] 0

# Gather the URLs for Male Results into a character vector, menURLS 
menURLs =
  c("cb99m.htm", "cb003m.htm", "results/2001/oof_m.html",
    "results/2002/oofm.htm", "results/2003/CB03-M.HTM",
    "results/2004/men.htm", "results/2005/CB05-M.htm",
   "results/2006/men.htm", "results/2007/men.htm",
   "results/2008/men.htm", "results/2009/09cucb-M.htm",
   "results/2010/2010cucb10m-m.htm",
    "results/2011/2011cucb10m-m.htm",
    "results/2012/2012cucb10m-m.htm")

# Reconstruct the urls vector to contain the proper Web Addresses
urls = paste(ubase, menURLs, sep = "")
urls[1:3]

# Print out the results again 
menTables = lapply(urls, extractResTable)

names(menTables) = 1999:2012

length(urls)

错误：preNode [[1]]中的错误：R

0 个答案: