在R中的前两个单词之后提取所有内容

Question

I am trying to extract all the info, using a regular expression in R, after the first number and first word of an entry in a data frame.

For example:

Header = 
c("2006 Volvo XC70", 
"2012 Ford Econoline Cargo Van E-250 Commercial", 
"2012 Nissan Frontier", 
"2012 Kia Soul 5dr Wagon Automatic")

I want to write a pattern that will grab Volvo XC70 , or Econoline Cargo Van E-250 Commercial (everything after the year and make) from an entry in my "header" column so that I may run the function on my data frame and create a new "model" column. I can't figure out a pattern that will allow me to skip the first string of integers, then a space, then the first string of characters, and then a space, and then grab everything proceeding.

Any help would be appreciated. Thanks!

Answer 1

Just use sub.

sub("^\\d+\\s+\\w+\\s+", "", df$x)

Example:

x <- "2012 Ford Econoline Cargo Van E-250 Commercial"
sub("^\\d+\\s+\\w+\\s+", "", x)
# [1] "Econoline Cargo Van E-250 Commercial"

Answer 2

For this task, I would fetch a basic list using the XML package:

library(XML)
doc <- xmlParse('http://www.fueleconomy.gov/ws/rest/ympg/shared/menu/make')

Now that we fetched the XML data we can create a vector with the car makes:

mk <- xpathSApply(doc, '//value', xmlValue)

Finally, I'll compile the pattern and play around with sprintf and sub :

df$Makes <- sub(sprintf('\\d+ (?:%s) ', paste(mk, collapse='|')), '', df$Header)

Output:

##                                          Header
# 1                                2006 Volvo XC70
# 2 2012 Ford Econoline Cargo Van E-250 Commercial
# 3                           2012 Nissan Frontier
# 4              2012 Kia Soul 5dr Wagon Automatic

##                                           Makes
# 1                                           XC70
# 2           Econoline Cargo Van E-250 Commercial
# 3                                       Frontier
# 4                       Soul 5dr Wagon Automatic