I need to extract the date from a dataframe of urls like these:
id | url
1 | https://www.infobae.com/tecno/2018/08/22/una-plataforma-argentina-entre-las-10-soluciones-de-big-data-mas-destacadas-del-ano/
2 | https://www.infobae.com/2014/08/03/1584584-que-es-data-lake-y-como-transforma-el-almacenamiento-datos/
3 | http://www.ellitoral.com/index.php/diarios/2018/01/09/economia1/ECON-02.html
4 | http://www.ellitoral.com/index.php/diarios/2017/12/01/economia1/ECON-01.html
5 | https://www.cronista.com/contenidos/2017/08/16/noticia_0089.html
6 | https://www.cronista.com/contenidos/2017/04/20/noticia_0090.html
7 | https://www.perfil.com/noticias/economia/supercomputadoras-para-sacarles-provecho-a-los-datos-20160409-0023.phtml
8 | https://www.mdzol.com/sociedad/100-cursos-online-gratuitos-sobre-profesiones-del-futuro-20170816-0035.html
9 | https://www.eldia.com/nota/2018-8-26-7-33-54--pueden-nuestros-datos-ponernos-en-serio-riesgo--revista-domingo
10 | https://www.letrap.com.ar/nota/2018-8-6-13-34-0-lula-eligio-a-su-vice-o-a-su-reemplazante
11 | https://www.telam.com.ar/notas/201804/270831-los-pacientes-deben-conocer-que-tipo-de-datos-usan-sus-medicos-coinciden-especialistas.html
12 | http://www.telam.com.ar/notas/201804/271299-invierten-100-millones-en-plataforma-de-internet-de-las-cosas.html
13 | http://www.telam.com.ar/notas/201308/30404-realizan-jornadas-sobre-tecnologia-para-gestion-de-datos.php
14 | http://www.telam.com.ar/notas/201701/176163-inteligencia-artificial-lectura-de-diarios.html
these urls have the date in different formats:
links 1-6 use /yyyy/mm/dd/
links 7-8 use -yyyymmdd-
links 9-10 use /yyyy-m-d-
links 11-14 use /yyyymm/
Luckily, these are all numbers (no "Jar" instead of 1).
Is there a regex that could extract them all, or most of them?
I believe the following regular expression does what you want.
regex <- "\\d{8}|\\d{6}|\\d{4}[^\\d]{1}\\d{2}|\\d{4}[^\\d]{1}\\d{1,2}[^\\d]{1}\\d{1,2}"
regmatches(URLData$url, regexpr(regex, URLData$url))
# [1] "2018/08/22" "2014/08/03" "2018/01/09" "2017/12/01" "2017/08/16"
# [6] "2017/04/20" "20160409" "20170816" "2018-8-26" "2018-8-6"
#[11] "201804" "201804" "201308" "201701"
Edit.
After reading the answer by @hrbrmstr I realized that it is probably better to coerce the results to class Date. I will use external package lubridate to do it.
d <- regmatches(URLData$url, regexpr(regex, URLData$url))
d[nchar(d) < 7] <- paste0(d[nchar(d) < 7], "01")
d <- lubridate::ymd(d)
d
# [1] "2018-08-22" "2014-08-03" "2018-01-09" "2017-12-01" "2017-08-16"
# [6] "2017-04-20" "2016-04-09" "2017-08-16" "2018-08-26" "2018-08-06"
#[11] "2018-04-01" "2018-04-01" "2013-08-01" "2017-01-01"
Data in dput format.
URLData <-
structure(list(id = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
13, 14), url = structure(c(10L, 9L, 2L, 1L, 7L, 6L, 13L, 12L,
8L, 11L, 14L, 5L, 3L, 4L), .Label = c(" http://www.ellitoral.com/index.php/diarios/2017/12/01/economia1/ECON-01.html",
" http://www.ellitoral.com/index.php/diarios/2018/01/09/economia1/ECON-02.html",
" http://www.telam.com.ar/notas/201308/30404-realizan-jornadas-sobre-tecnologia-para-gestion-de-datos.php",
" http://www.telam.com.ar/notas/201701/176163-inteligencia-artificial-lectura-de-diarios.html ",
" http://www.telam.com.ar/notas/201804/271299-invierten-100-millones-en-plataforma-de-internet-de-las-cosas.html",
" https://www.cronista.com/contenidos/2017/04/20/noticia_0090.html",
" https://www.cronista.com/contenidos/2017/08/16/noticia_0089.html",
" https://www.eldia.com/nota/2018-8-26-7-33-54--pueden-nuestros-datos-ponernos-en-serio-riesgo--revista-domingo",
" https://www.infobae.com/2014/08/03/1584584-que-es-data-lake-y-como-transforma-el-almacenamiento-datos/",
" https://www.infobae.com/tecno/2018/08/22/una-plataforma-argentina-entre-las-10-soluciones-de-big-data-mas-destacadas-del-ano/",
" https://www.letrap.com.ar/nota/2018-8-6-13-34-0-lula-eligio-a-su-vice-o-a-su-reemplazante",
" https://www.mdzol.com/sociedad/100-cursos-online-gratuitos-sobre-profesiones-del-futuro-20170816-0035.html",
" https://www.perfil.com/noticias/economia/supercomputadoras-para-sacarles-provecho-a-los-datos-20160409-0023.phtml",
" https://www.telam.com.ar/notas/201804/270831-los-pacientes-deben-conocer-que-tipo-de-datos-usan-sus-medicos-coinciden-especialistas.html"
), class = "factor")), class = "data.frame", row.names = c(NA,
-14L))