web scraping in imdb using R

Question

I want to find the link to the top 250 movies in imdb. I decided to find a common pattern by viewing the HTML source code. I found "chttp" but I am not sure if it will get me anywhere. How can I find a pattern to construct the links upon it?

require("XML")
imdb="http://www.imdb.com/chart/top?sort=ir,desc"
imdb.page=readLines(imdb)
g = grep(pattern = "chttp", x = imdb_page) 
imdb.lines=imdb.page[g]

Here's an example output:

> imdb.lines[1]
[1] "      <h3><a href=\"/chart/?ref_=chttp_cht\" >IMDb Charts</a></h3>"

My main problem is trying to figure out the link(URL) for each of the 250 top movies based on the code I have already written. I basically don't know what's the next step. Also I am not sure the pattern I used the grep command for "chttp" is a good one at all or not.

So according to results starting from index 3 the movie titles are on the odd indices:

> imdb.lines[1]
[1] "      <h3><a href=\"/chart/?ref_=chttp_cht\" >IMDb Charts</a></h3>"
> imdb.lines[2]
[1] "  <td class=\"posterColumn\"><a href=\"/title/tt0111161/?ref_=chttp_tt_1\" ><img src=\"http://ia.media-imdb.com/images/M/MV5BODU4MjU4NjIwNl5BMl5BanBnXkFtZTgwMDU2MjEyMDE@._V1_SX34_CR0,0,34,50_.jpg\" width=\"34\" height=\"50\" />"
> imdb.lines[3]
[1] "    <a href=\"/title/tt0111161/?ref_=chttp_tt_1\" title=\"Frank Darabont (dir.), Tim Robbins, Morgan Freeman\" >The Shawshank Redemption</a>"
> imdb.lines[6]
[1] "  <td class=\"posterColumn\"><a href=\"/title/tt0071562/?ref_=chttp_tt_3\" ><img src=\"http://ia.media-imdb.com/images/M/MV5BNDc2NTM3MzU1Nl5BMl5BanBnXkFtZTcwMTA5Mzg3OA@@._V1_SX34_CR0,0,34,50_.jpg\" width=\"34\" height=\"50\" />"
> imdb.lines[4]
[1] "  <td class=\"posterColumn\"><a href=\"/title/tt0068646/?ref_=chttp_tt_2\" ><img src=\"http://ia.media-imdb.com/images/M/MV5BMjEyMjcyNDI4MF5BMl5BanBnXkFtZTcwMDA5Mzg3OA@@._V1_SX34_CR0,0,34,50_.jpg\" width=\"34\" height=\"50\" />"
> imdb.lines[5]
[1] "    <a href=\"/title/tt0068646/?ref_=chttp_tt_2\" title=\"Francis Ford Coppola (dir.), Marlon Brando, Al Pacino\" >The Godfather</a>"
> imdb.lines[7]
[1] "    <a href=\"/title/tt0071562/?ref_=chttp_tt_3\" title=\"Francis Ford Coppola (dir.), Al Pacino, Robert De Niro\" >The Godfather: Part II</a>"
> imdb.lines[9]
[1] "    <a href=\"/title/tt0468569/?ref_=chttp_tt_4\" title=\"Christopher Nolan (dir.), Christian Bale, Heath Ledger\" >The Dark Knight</a>"
> imdb.lines[10]
[1] "  <td class=\"posterColumn\"><a href=\"/title/tt0110912/?ref_=chttp_tt_5\" ><img src=\"http://ia.media-imdb.com/images/M/MV5BMjE0ODk2NjczOV5BMl5BanBnXkFtZTYwNDQ0NDg4._V1_SY50_CR0,0,34,50_.jpg\" width=\"34\" height=\"50\" />"

Answer 1

xpath makes jobs like this trivial.

library(XML)
tt <- htmlParse('http://www.imdb.com/chart/top?sort=ir,desc')
cbind(xpathSApply(tt, "//td[@class='titleColumn']//a", xmlValue),
           t(xpathSApply(tt, "//td[@class='titleColumn']//a", xmlAttrs)))

The first argument to cbind returns titles (the text between the a tags) and the second returns the anchors' attributes (href and title, the latter of which in this case contains details about the films' directors).

Answer 2

What about using the alternative interfaces?

Edit #1: I have looked into some of the files and there don't seem to be any links or even the imdb ID, there should be another way though.

Edit #2: OK, there is no other way apparently, but somebody already did something. E.g. this guy; have a look.