Extracting strings from links using regex in R

Question

I have a list of url links and i want to extract one of the strings and save them in another variable. The sample data is below:

  sample<-  c("http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr01f2009.pdf",
            "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr02f2001.pdf",
           "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr03f2002.pdf",
          "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr04f2004.pdf",
         "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr05f2005.pdf",
           "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr06f2018.pdf",
           "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr07f2016.pdf",
            "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr08f2015.pdf",
          "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr09f2020.pdf",
             "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr10f2014.pdf")

sample

 [1] "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr01f2009.pdf"
 [2] "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr02f2001.pdf"
 [3] "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr03f2002.pdf"
 [4] "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr04f2004.pdf"
 [5] "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr05f2005.pdf"
 [6] "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr06f2018.pdf"
 [7] "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr07f2016.pdf"
 [8] "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr08f2015.pdf"
 [9] "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr09f2020.pdf"
[10] "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr10f2014.pdf"

I want to extract week and year using regex.

     week year
1     1 2009
2     2 2001
3     3 2002
4     4 2004
5     5 2005
6     6 2018
7     7 2016
8     8 2015
9     9 2020
10   10 2014

score 1 · Accepted Answer · answered Aug 28 '20 at 03:01

You could use str_match to capture numbers after 'owgr' and 'f' :

library(stringr)
str_match(sample, 'owgr(\\d+)f(\\d+)')[, -1]

You can convert this to dataframe, change class to numeric and assign column names.

setNames(type.convert(data.frame(
          str_match(sample, 'owgr(\\d+)f(\\d+)')[, -1])), c('year', 'week'))

#   year week
#1     1 2009
#2     2 2001
#3     3 2002
#4     4 2004
#5     5 2005
#6     6 2018
#7     7 2016
#8     8 2015
#9     9 2020
#10   10 2014

Another way could be to extract all the numbers from last part of sample. We can get the last part with basename.

str_extract_all(basename(sample), '\\d+', simplify = TRUE)

Tho Vu · Answer 2 · 2020-08-28T03:53:19.950

1

Another way you can try

library(dplyr)
library(stringr)
df <- data.frame(sample)
df2 <- df %>% 
  transmute(year = str_extract(sample, "(?<=wgr)\\d{1,2}(?=f)"), week = str_extract(sample, "(?<=f)\\d{4}(?=\\.pdf)"))

#     year week
# 1     1 2009
# 2     2 2001
# 3     3 2002
# 4     4 2004
# 5     5 2005
# 6     6 2018
# 7     7 2016
# 8     8 2015
# 9     9 2020
# 10   10 2014

edited Aug 28 '20 at 03:53

answered Aug 28 '20 at 03:31

Tho Vu

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score 0 · Answer 3 · answered Sep 26 '20 at 00:13

You could use {unglue} :

library(unglue)

unglue_data(
  sample,
  "http://dps.endavadigital.net/owgr/doc/content/archive/2009/owgr{week}f{year}.pdf")
#>    week year
#> 1    01 2009
#> 2    02 2001
#> 3    03 2002
#> 4    04 2004
#> 5    05 2005
#> 6    06 2018
#> 7    07 2016
#> 8    08 2015
#> 9    09 2020
#> 10   10 2014

Extracting strings from links using regex in R

3 Answers3