install.packages(“stringr”,repos=‘http://mirrors.nics.utk.edu/cran/’) library(stringr)

  1. Copy the introductory example. The vector name stores the extracted names.
raw.data <- "555-1239Moe Szyslak(636) 555-0113Burns, C. Montgomery555-6542Rev. Timothy Lovejoy555 8904Ned Flanders636-555-3226Simpson,Homer5553642Dr. Julius Hibbert"

name <- unlist(str_extract_all(raw.data, "[[:alpha:]., ]{2,}"))
name
## [1] "Moe Szyslak"          "Burns, C. Montgomery" "Rev. Timothy Lovejoy"
## [4] "Ned Flanders"         "Simpson,Homer"        "Dr. Julius Hibbert"
phone <- unlist(str_extract_all(raw.data, "\\(?(\\d{3})?\\)?(-| )?\\d{3}(-| )?\\d{4}"))
phone
## [1] "555-1239"       "(636) 555-0113" "555-6542"       "555 8904"      
## [5] "636-555-3226"   "5553642"
data.frame(name = name, phone = phone)
##                   name          phone
## 1          Moe Szyslak       555-1239
## 2 Burns, C. Montgomery (636) 555-0113
## 3 Rev. Timothy Lovejoy       555-6542
## 4         Ned Flanders       555 8904
## 5        Simpson,Homer   636-555-3226
## 6   Dr. Julius Hibbert        5553642
  1. Use the tools of this chapter to rearrange the vector so that all elements conform to the standard first_name last_name.
# First name - strings with commas
firtcomma <- str_trim(str_sub(name, start = str_locate(name, ",")[,1] + 1, end = str_length(name)))

# First name - strings without commas and a single space
firstspace <- str_sub(name, start = 1, end = str_locate(name, " ")[,1] - 1)

# Last name - strings with commas
lastcomma <- str_trim(str_sub(name, start = 1, end = str_locate(name, ",")[,1] - 1))

# Last name - strings without commas and a single space
lastspace <- str_sub(name, start = str_locate(name, " ")[,1] + 1, end = str_length(name))

# Everything after the first space for all strings
afterspace <- str_sub(name, start = str_locate(name, " ")[,1] + 1, end = str_length(name))

# Extract First_Name
firstname <- ifelse(str_detect(name, ","), firtcomma, ifelse(str_count(name, " ") == 2, ifelse(str_detect(afterspace, " "), str_sub(afterspace, start = 1, end = str_locate(afterspace, " ")[,1] - 1), afterspace), firstspace))

# Extract_Last_Name
lastname <- ifelse(str_detect(name, ","), lastcomma, ifelse(str_count(name, " ") == 2, ifelse(str_detect(afterspace, " "), str_sub(afterspace, start = str_locate(afterspace, " ")[,1] + 1, end = str_length(afterspace)), afterspace), lastspace))

# Formatted name
fullname <- str_c(firstname, " ", lastname)
fullname
## [1] "Moe Szyslak"         "C. Montgomery Burns" "Timothy Lovejoy"    
## [4] "Ned Flanders"        "Homer Simpson"       "Julius Hibbert"
  1. Construct a logical vector indicating whether a character has a title (i.e., Rev. and Dr.).
# search for the presence of a title
str_detect(name, "Maid|Madam|Mx.|Ms.|Miss|Mrs.|Mr.|Mister|Rev.|Reverend|Dr.|Doctor|Prof.|Professor|Father|Hon.|Honorable|Pres.|President|Gov.|Governer|Msgr.|Monsignor|Sen.|Senator")
## [1] FALSE FALSE  TRUE FALSE FALSE  TRUE
  1. Construct a logical vector indicating whether a character has a second name.
name_count <- name

str_count(str_trim(str_replace_all(name_count, "Maid|Madam|Mx.|Ms.|Miss|Mrs.|Mr.|Mister|Rev.|Reverend|Dr.|Doctor|Prof.|Professor|Father|Hon.|Honorable|Pres.|President|Gov.|Governer|Msgr.|Monsignor|Sen.|Senator", "")), " ") > 1
## [1] FALSE  TRUE FALSE FALSE FALSE FALSE
  1. Describe the types of strings that conform to the following regular expressions and construct an example that is matched by the regular expression.

  1. [0-9]+\$

    This expressions extracts digits/numerals from 0-9 followed by a dollar sign $.
amount <- "This laptop cost 999$ after a 20% discount from the manufacturer."
cost <- (unlist(str_extract_all(amount, "[0-9]+\\$")))
cost
## [1] "999$"

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

    This expression extracts all words that are both lowercase and have a maximum length of 4 characters and a minimum of 1 character.
amount <- "This laptop cost 999$ after a 20% discount from the manufacturer."
item <- (unlist(str_extract_all(amount, "\\b[a-z]{1,4}\\b")))
item
## [1] "cost" "a"    "from" "the"

  1. .*?\.txt$

    This expression extracts all statements ending in .txt preceded by any number of characters or none.
note that the statement "txt" without the period (.) does not print out.
# Create example strings that end in .txt
t <- c("..txt", "txt", ".txt","alpha.txt","test.txt", "huge.txt", "99999.txt")

unlist(str_extract_all(t, ".*?\\.txt$"))
## [1] "..txt"     ".txt"      "alpha.txt" "test.txt"  "huge.txt"  "99999.txt"

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

    This expression extracts dates of the format xx/xx/xxxx.
amount <- "This laptop cost 999$ after a 20% discount from the manufacturer. The date of manufacture is noted as 12/12/2019 although the actual assembly date was 12/12/2020."
item <- (unlist(str_extract_all(amount, "\\d{2}/\\d{2}/\\d{4}")))
item
## [1] "12/12/2019" "12/12/2020"

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

    This expression extracts HTML tagged lines that opens in <> and closes with </>. Any HTML tag that doesnt close in </> will not be extracted. An image tag would not print out.
# Create example strings of a HTML nature
t <- c("<h1>Report Heading</h1>","<h1></h1>","<p>S. Kigamba<br>89 Born<br>Kenya</p>","<img src='school.gif' alt='School library' height='20' width='60'>")
unlist(str_extract_all(t, "<(.+?)>.+?</\\1>"))
## [1] "<h1>Report Heading</h1>"              
## [2] "<p>S. Kigamba<br>89 Born<br>Kenya</p>"
  1. The following code hides a secret message. Crack it with R and regular expressions. Hint: Some of the characters are more revealing than others! The code snippet is also available in the materials at www.r-datacollection.com.
rawdata <- ("clcopCow1zmstc0d87wnkig7OvdicpNuggvhryn92Gjuwczi8hqrfpRxs5Aj5dwpn0Tanwo
Uwisdij7Lj8kpf03AT5Idr3coc0bt7yczjatOaootj55t3Nj3ne6c4Sfek.r1w1YwwojigO
d6vrfUrbz2.2bkAnbhzgv4R9i05zEcrop.wAgnb.SqoU65fPa1otfb7wEm24k6t3sR9zqe5
fy89n6Nd5t9kc4fE905gmc4Rgxo5nhDk!gr")
message <- unlist(str_extract_all(rawdata, "[[:upper:].]"))
combine <- paste(message, collapse = '')
#combine
secret_message <- str_replace_all(combine, "\\.", " ")
secret_message
## [1] "CONGRATULATIONS YOU ARE A SUPERNERD"