Manipulating Strings

Input Names

library("stringr")
name <- c("Moe Szyslak", "Burns, C. Montogomery", "Rev. Timothy Lovejoy", "Ned Flanders", "Simpson, Homer", "Dr. Julius Hibbert")

Extract Last Names - Question 3A

last_name <-unlist(str_extract_all(name, "[[:alpha:]]{2,},|[^[\\.]][[:blank:]][[:alpha:]]{3,}"))
last_name <-unlist(str_extract_all(last_name, "[[:alpha:]]{2,}"))
last_name

## [1] "Szyslak"  "Burns"    "Lovejoy"  "Flanders" "Simpson"  "Hibbert"

Extract First Names

first_name <-unlist(str_extract_all(name, ", [[:alpha:]]{2,}|[[:upper:]]{1}. [[:alpha:]]{2,}|[[:alpha:]]{3,}[[:blank:]]"))
first_name <-unlist(str_extract_all(first_name, "[[:alpha:]]{2,}|[[:upper:]]{1}. [[:alpha:]]{2,}"))
first_name

## [1] "Moe"            "C. Montogomery" "Timothy"        "Ned"           
## [5] "Homer"          "Julius"

Write Names in Data Frame

name_table <- data.frame (first_name, last_name)
name_table

##       first_name last_name
## 1            Moe   Szyslak
## 2 C. Montogomery     Burns
## 3        Timothy   Lovejoy
## 4            Ned  Flanders
## 5          Homer   Simpson
## 6         Julius   Hibbert

Logical Vector to indicate title Question 3B

title <- str_detect(name, "[[:upper:]]{1}[[:alpha:]]{1,}\\.")
name_table <- cbind(name_table, title)
name_table

##       first_name last_name title
## 1            Moe   Szyslak FALSE
## 2 C. Montogomery     Burns FALSE
## 3        Timothy   Lovejoy  TRUE
## 4            Ned  Flanders FALSE
## 5          Homer   Simpson FALSE
## 6         Julius   Hibbert  TRUE

Logical Vector to indicate a second name Question 3C

two_names <- str_detect(first_name, "[[:upper:]]{1}\\. [[:alpha:]]{1,}")
name_table <- cbind(name_table, two_names)
name_table

##       first_name last_name title two_names
## 1            Moe   Szyslak FALSE     FALSE
## 2 C. Montogomery     Burns FALSE      TRUE
## 3        Timothy   Lovejoy  TRUE     FALSE
## 4            Ned  Flanders FALSE     FALSE
## 5          Homer   Simpson FALSE     FALSE
## 6         Julius   Hibbert  TRUE     FALSE

Question 4

Describe the types of strings that confom to the following regular expressons and construct an example that is matched by the regular expression.

1. [0-9]+\$

   a digit between 0 and 9 that is repeated one or more times followed by $

   example: 45$

a <- "45$"
str_extract_all(a, "[0-9]+\\$")

## [[1]]
## [1] "45$"

2. \b[a-z]{1,4}\b

   a string that begins with a lower case letter that appears at least once but no more than 4 times followed by where the number is the end of the string

   example: yes

b <- "yes"
str_extract_all(b, "\\b[a-z]{1,4}\\b")

## [[1]]
## [1] "yes"

3. .*?\.txt$

   a single character matched zero or more times (the preceeding item is optional and will be matched at most once) followed by a period and followed by txt

   example: file.txt

c <- "file.txt"
str_extract_all(c, ".*?\\.txt$")

## [[1]]
## [1] "file.txt"

4. \d{2}/\d{2}/\d{4}

   a two digit number followed by / followed by a 2 digit number followed by / followed by a 4 digit number … a date

   example: 11/12/1985

d <- "11/12/1985"
str_extract_all(d, "\\d{2}/\\d{2}/\\d{4}")

## [[1]]
## [1] "11/12/1985"

5. <(.+?)>.+?</\1>

   a string that starts with < which is followed by one or more characters and then followed by > which is followed by at least 1 character which is followed by the repeat of the first set of characters in sideways brackets preceeded by /

   example:

   heading

e <- "<h1>heading</h1>"
str_extract_all(e, "<(.+?)>.+?</\\1>")

## [[1]]
## [1] "<h1>heading</h1>"