Regex in R

##%######################################################%##
#                                                          #
####               Regex in R - Your Turn               ####
#                                                          #
##%######################################################%##


# Match the following regular expressions against the test vector below using `str_detect`.  
## Can you explain the matches?

# Regular expressions

# 1. ^dog
# 2. ^[a-z]+$
# 3. \\d

test_vector <- c("Those dogs are small.","dogs and cats",
                 "34","(34)","rat","watchdog","placemat",
                 "BABY","2011_April","mice")


# load packages -----------------------------------------------------------
library(stringr)

# create text string ------------------------------------------------------
test_vector <- c("Those dogs are small.","dogs and cats",
                 "34","(34)","rat","watchdog","placemat",
                 "BABY","2011_April","mice")

# evaluate if each element contains a match -------------------------------
# match the literal string dog
str_detect(test_vector,"^dog") # second element contains match

# match lowercase
str_detect(test_vector,"^[a-z]+$") # elements 5,6,7, and 10 matched 

# match numbers
str_detect(test_vector,"\\d") # elements 3,4, and 9 matched