Working with strings in R

stringr.R

# install
install.packages('stringr')
install.packages('readr')
install.packages('tibble')
install.packages('magrittr')
install.packages('purrr')
install.packages('dplyr')

# library
library(stringr)
library(readr)
library(tibble)
library(magrittr)
library(purrr)
library(dplyr)

# import data
mockstring <- readr::read_csv('https://raw.githubusercontent.com/rsquaredacademy/datasets/master/mock_strings.csv')
mockstring

# extract domain name from random email ids
mockstring$email[1:2] %>% 
  str_split(pattern = '@') %>%
  unlist() %>%
  str_subset(pattern = '\\.') %>%
  str_split(pattern = '\\.') %>%
  purrr::map_chr(extract(1))

# extract image type from url
mockstring$imageurl[1:5] %>%
  str_split(pattern = '\\.') %>%
  purrr::map_chr(extract(3)) %>%
  str_sub(start = 1, end = 3)

mockstring$imageurl[1:5] %>%
  str_split(pattern = '\\.') %>%
  purrr::map_chr(extract(3)) %>%
  str_split(pattern = '/') %>%
  purrr::map_chr(extract(1))

# extract image dimension from url
pattern <- "[:digits:]"
mockstring$imageurl[1:5] %>%
  str_locate(pattern = "[0-9]") 
  
mockstring$imageurl[1:5] %>%
  str_sub(start = 23) %>%
  str_split(pattern = '\\.') %>%
  purrr::map_chr(extract(1))

# extract protocol
mockstring$url[1:5] %>%
  str_split(pattern = '://') %>%
  map_chr(extract(1))
  
k <- mockstring$url[1:5] %>%
  str_locate(pattern = '://') %>%
  data.frame() %>%
  extract2('start') %>%
  subtract(1)

mockstring$url[1:5] %>%
  str_sub(start = 1, end = k)

# extract domain name
n <- mockstring$url[1:5] %>%
  str_locate_all(pattern = "/") %>%
  map_int(extract(3))

mockstring$url[1:5] %>%
  str_sub(end = n) %>%
  str_split(pattern = '\\.') %>%
  map_chr(extract(1)) %>%
  str_sub(start = k + 4)

# extract extension from url
mockstring$url[1:5] %>%
  str_sub(end = n) %>%
  str_split(pattern = '\\.') %>%
  map_chr(extract(2)) %>%
  str_split(pattern = '/') %>%
  map_chr(extract(1))

# extract file type from url
# only 2 dots in the url
mockstring$url[1:3] %>%
  str_locate_all(pattern = '\\.') %>%
  map_int(nrow) %>%
  is_greater_than(2) %>%
  sum()
  
# only 1 question mark in the url
mockstring$url[1:3] %>%
  str_locate_all(pattern = "[?]") %>%
  map_int(nrow) %>%
  is_greater_than(1) %>%
  sum()

# location of second dot and 1 question mark
d <- mockstring$url[1:3] %>%
  str_locate_all(pattern = '\\.') %>%
  map_int(extract(2)) %>%
  add(1)

q <- mockstring$url[1:3] %>%
  str_locate_all(pattern = "[?]") %>%
  map_int(extract(1)) %>%
  subtract(1)

mockstring$url[1:3] %>% 
  str_sub(start = d, end = q)