Question

I have a file with two columns, one has the content type of HTTP objects like text/html, application/rar etc and the other has the bytes size.

Content Type                                     Size
video/x-flv                                       100
image/jpeg                                        150
text/html                                         160
application/octet-stream                          200  
application/x-shockwave-flash                     ...
text/plain
application/x-javascript
text/xml
text/css
text/html; charset=utf-8
application/x-javascript; charset=utf-8           ...

As you can see there are many variations of the same content type, such as application/x-javascript and application/x-javascript; charset=utf-8 and so on. So, I would like to create another column to categorize them more generically. So, that these two would just be web/javascript and so on.

 Content Type                                      Size      Category
    video/x-flv                                       100       web/video
    image/jpeg                                        150       web/image
    text/html                                         160       web/html
    application/octet-stream                          200       web/binary
    application/x-shockwave-flash                     ...       web/flash
    text/plain                                                  web/plaintext
    application/x-javascript                                    web/javascript
    video/x-msvideo                                             web/video
    text/xml                                                    web/xml
    text/css                                                    web/css
    text/html; charset=utf-8                                    web/html
    video/quicktime                                             web/video
    application/x-javascript; charset=utf-8                     web/javascript

How would I accomplish this in R and I presume I need to use regular expressions of some sort for this?

Answer 1

There are several ways you can simplify your variable. Here I will use the stringr package for string manipulation functions :

R> library(stringr)

First, copy your content type variable into a new character variable :

R> d <- data.frame(type=c("video/x-flv", "image/jpeg","video/x-msvideo", "application/x-javascript; charset=utf-8", "application/x-javascript"))
R> d$type2 <- as.character(d$type)

Which just gives you :

                                     type                                   type2
1                             video/x-flv                             video/x-flv
2                              image/jpeg                              image/jpeg
3                         video/x-msvideo                         video/x-msvideo
4 application/x-javascript; charset=utf-8 application/x-javascript; charset=utf-8
5                application/x-javascript                application/x-javascript

Then you can work on your new variable. You can just replace manually certain type value by another :

R> d$type2[d$type2 == "video/x-flv"] <- "video"
R> d
                                     type                                   type2
1                             video/x-flv                                   video
2                              image/jpeg                              image/jpeg
3                         video/x-msvideo                         video/x-msvideo
4 application/x-javascript; charset=utf-8 application/x-javascript; charset=utf-8
5                application/x-javascript                application/x-javascript

You can use regexp matching to replace all the values matching, for example, “video” :

R> d$type2[str_detect(d$type2, ".*video.*")] <- "video"
R> d
                                     type                                   type2
1                             video/x-flv                                   video
2                              image/jpeg                              image/jpeg
3                         video/x-msvideo                                   video
4 application/x-javascript; charset=utf-8 application/x-javascript; charset=utf-8
5                application/x-javascript                application/x-javascript

Or you can use regexp replacement to clean certain values. For example by removing everything behind the “;” in your content types :

R> d$type2 <- str_replace(d$type2, ";.*$", "")
R> d
                                     type                    type2
1                             video/x-flv                    video
2                              image/jpeg               image/jpeg
3                         video/x-msvideo                    video
4 application/x-javascript; charset=utf-8 application/x-javascript
5                application/x-javascript application/x-javascript

Be careful of the order of your instructions, though, as your result highly depends on it.