no applicable method for 'xpathApply' applied to an object of class "NULL"

Question

I have the following code I don't know why I receive this error:

rm(list=ls())
require("XML")
# <a href="/music/The+Beatles/Sgt.+Pepper%27s+Lonely+Hearts+Club+Band" 
beatles = "http://www.last.fm/music/The+Beatles/"

beatles.albums.page = paste(sep="", beatles, "+albums")
lines = readLines(beatles.albums.page)
album.lines = grep(pattern="href.*link-reference", lines, value=TRUE)
album.names = sub(pattern=".*<h3>(.*)</h3>.*", replacement="\\1", x=album.lines)
album.names = gsub(pattern=" ", replacement="+", x=album.names)
album.names = gsub(pattern="'", replacement="%27", x=album.names)

for (album in album.names[1]) {
  print(album)
  album.link = paste(sep="", beatles, album)
  print(album.link)
  tables = readHTMLTable(album.link)

}

Any idea?

last.fm does have an API - http://www.last.fm/api - that would make this *much* cleaner than scraping. — hrbrmstr, Apr 01 '14 at 19:07

Fernando · Accepted Answer · 2014-04-01T19:06:12.247

The line

readHTMLTable(album.link)

is causing the error. Try changing it to

tables = readHTMLTable(album.link, header = FALSE)

But it still gives you the warning:

Warning message:
In readLines(beatles.albums.page) :
  incomplete final line found on 'http://www.last.fm/music/The+Beatles/+albums'

Which you can get rid with

readLines(beatles.albums.page, warn = FALSE)

Also note that you're not 'saving' the tables, it changes at every loop, but maybe that's what you want.

no applicable method for 'xpathApply' applied to an object of class "NULL"

1 Answers1