Shifting text around in a sentence via R - r

Question

I have an R dataframe with movie names like so:
Shawshank Redemption, The
Godfather II, The
Band of Brothers
I would like to display these names as:
The Shawshank Redemption
The Godfather II
Band of Brothers
Can anyone help with how to do a check each row of the dataframe to see if there is a 'The' after a comma (like) above, and if there is, shift it to the front of the sentence?

Answer 1

You can use gsub:
df$movies2 = gsub("^([\\w\\s]+),*\\s*([Tt]he*($|(?=\\s\\(\\d{4}\\))))", "\\2 \\1", df$movies, perl = TRUE)
Result:
> df
movies movies2
1 Shawshank Redemption, The (1994) The Shawshank Redemption (1994)
2 Godfather II, The The Godfather II
3 Band of Brothers Band of Brothers
4 Dora, The Explorer Dora, The Explorer
5 Kill Bill Vol. 2 The Kill Bill Vol. 2 The
6 ,The Highlander ,The Highlander
7 Happening, the the Happening
Data:
df = data.frame(movies = c("Shawshank Redemption, The (1994)",
"Godfather II, The",
"Band of Brothers",
"Dora, The Explorer",
"Kill Bill Vol. 2 The",
",The Highlander",
"Happening, the"), stringsAsFactors = FALSE)
Notes:
The goal of the entire regex is to group the first part (part before ,) and the second part ('The' after , and only when it's at the end or before (year)) into separate capture groups which I can swap with \\2 and \\1
^([\\w\\s]+) matches any word character or spaces one or more times starting from the beginning of the string
,*\\s* matches comma and space both zero or more times
[Tt]he* matches "The" or "the" zero or more times
Notice that it is followed by ($|(?=\\s\\(\\d{4}\\))) which matches the "end of string", $, or a positive lookahead, which checks whether the previous pattern is followed by \\s\\(\\d{4}\\)
\\s\\(\\d{4}\\) matches a space and (4 digits) including the parentheses. Double backslashes are needed to escape a single backslash
So ([Tt]he*($|(?=\\s\\(\\d{4}\\)))) matches "The" or "the" either at the end of string or if it is followed by (4 digits)
Everything in parentheses are capture groups, so \\2 \\1 swaps the first capture group, ([\\w\\s]+), with the second, ([Tt]he*($|(?=\\s\\(\\d{4}\\))))
Now, since "The" is only matched zero or more times by [Tt]he*, if a string doesn't have "The" in it, an empty string gets swapped, with \\1, which returns the original string.

Answer 2

This seems to work for me:
#create a vector of movies
x=c("Shawshank Redemption, The", "Godfather II, The", "Band of Brothers")
#use grep to find those with ", The" at the end
the.end=grep(", The$",x)
#trim movie titles to remove ", The"
trimmed=strtrim(x[the.end],nchar(x[the.end])-5)
#add "The " to the beginning of the trimmed titles
final=paste("The",trimmed)
#replace the trimmed elements of the movie vector
x[the.end]<-final
#take a look
x
Note that this doesn't remove ", The" from anywhere in the name other than the end... I think that's the behaviour that you want. It will also miss any "The" without the comma, or lower case "the". To see what I mean, try this as your initial movie vector:
#create a vector of movies
x=c("Shawshank Redemption, The", "Godfather II, The", "Band of Brothers",
"Dora, The Explorer", "Kill Bill Vol. 2 The", ",The Highlander",
"Happening, the")