Basic String Handling

Basic String Handling

This is the Markdown file for the my third homework assignment. The problem statement is as follows:

Before we begin, let’s get this library stringr

library(stringr)

## Warning: package 'stringr' was built under R version 3.6.3

Problem 3: Copy the introductory example.

1. Use the tools…..

Yank given string into program variable raw.data:

raw.data <-"555-1239Moe Szyslak(636) 555-0113Burns, C. Montgomery555-6542Rev. Timothy Lovejoy555 8904Ned Flanders636-555-3226Simpson, Homer5553642Dr. Julius Hibbert"

Remove some non-alpha characters e.g. numbers, brackets, hyphens:

name <- unlist(str_extract_all(raw.data, "[^[:digit:]^[-()]]{2,}"))
name

## [1] "Moe Szyslak"          "Burns, C. Montgomery" "Rev. Timothy Lovejoy"
## [4] "Ned Flanders"         "Simpson, Homer"       "Dr. Julius Hibbert"

Remove “C.”, “Rev. ”, “Dr. ”, and “,”. Piped the processes with “>%”. It’s like the Unix/Linux pipe “|”. It’s not mentioned in the chapter, but I looked up.

name1 <- str_replace(name, pattern = "C. ", "") %>% str_replace(pattern = "Rev. ", "") %>% str_replace(pattern = "Dr. ", "") %>% str_replace(pattern = "[,]", "")
name1

## [1] "Moe Szyslak"      "Burns Montgomery" "Timothy Lovejoy"  "Ned Flanders"    
## [5] "Simpson Homer"    "Julius Hibbert"

Split first_name and last_name.

name.df <- data.frame(str_split_fixed(name1, "[[:blank:]]", 2))

Creating heading.

name.hd <- c("first_name", "last_name")
names(name.df) <- name.hd

Print names.df, with proper heading and formatting.

print(name.df, right=F)

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

2. Construct a logical vector ….. has a title (i.e., Rev. and Dr.)

Logical vector to find Dr. or Rev.

str_detect(name, "[DR][re][.v]")

## [1] FALSE FALSE  TRUE FALSE FALSE  TRUE

3. Construct a logical vector ….. has a second name.

Logical vector to find middle name C., as in one case. This is done differently from the previous one.

str_detect(name, "[:SPACE:][[:alpha:]]{1}[\\.]")

## [1] FALSE  TRUE FALSE FALSE FALSE FALSE

Problem 4: Describe the types of strings…..

1. [0-9]+\$ : Anywhere in the string, there has to be numeric character, immediately followed by the \(-character, e.g. "CCCC4\)BBB".

str <- c("CCCC4$BBB", "CCCC4BBB$","CCCC4BBB$")
str_detect(str, "[0-9]+\\$")

## [1]  TRUE FALSE FALSE

2. \b[a-z]{1,4}\b : Anywhere in the string, there has to be a lowercase word (i.e. a preceded and followed by white space), which is at least one character long but at most 4 characters.

str <- c("A 22g uShy Try KKKK", "LLLL kkkl LLL MMMM", "CCCC4BBB$ hhhP")
str_detect(str, "\\b[a-z]{1,4}\\b")

## [1] FALSE  TRUE FALSE

3. .*?\.txt$ : The string has to end with .txt.

str <- c("A 22g uShy Try KKKK.txt", "LLLL kkkl.txt LLL MMMM", "CCCC4BBB$ hhhP")
str_detect(str, ".*?\\.txt$")

## [1]  TRUE FALSE FALSE

4. \d{2}/\d{2}/\d{4} : The string must contain nn/nn/nnnn, where n stands for numeric.

str <- c("A 02/12/9988 KKKK.txt", "LLLL 88/33/9878 SDDD.txt LLL MMMM", " 77-99-676")
str_detect(str, "\\d{2}/\\d{2}/\\d{4}")

## [1]  TRUE  TRUE FALSE

5. <(.+?)>.+?</\1> : The following example will exemplify better than a wordy description.

str <- c("LLLL <hkLd1> this is string</hkLd1>  lljlj", "<p>Wall Street</pt>", "<man>j</man")
str_detect(str, "<(.+?)>.+?</\\1>")

## [1]  TRUE FALSE FALSE

Problem 9: Secret message.

First yank the string, containing secret message, into program variable

password_string <- c("clcopCow1zmstc0d87wnkig7OvdicpNuggvhryn92Gjuwczi8hqrfpRxs5Aj5dwpn0Tanwo
Uwisdij7Lj8kpf03AT5Idr3coc0bt7yczjatOaootj55t3Nj3ne6c4Sfek.r1w1YwwojigO
d6vrfUrbz2.2bkAnbhzgv4R9i05zEcrop.wAgnb.SqoU65fPa1otfb7wEm24k6t3sR9zqe5
fy89n6Nd5t9kc4fE905gmc4Rgxo5nhDk!gr")
password_string

## [1] "clcopCow1zmstc0d87wnkig7OvdicpNuggvhryn92Gjuwczi8hqrfpRxs5Aj5dwpn0Tanwo\nUwisdij7Lj8kpf03AT5Idr3coc0bt7yczjatOaootj55t3Nj3ne6c4Sfek.r1w1YwwojigO\nd6vrfUrbz2.2bkAnbhzgv4R9i05zEcrop.wAgnb.SqoU65fPa1otfb7wEm24k6t3sR9zqe5\nfy89n6Nd5t9kc4fE905gmc4Rgxo5nhDk!gr"

It’s visible that there are some capitalized characters, and mostly small characters. Let’s try to extract those capitalized characters.

message <- unlist(str_extract_all(password_string,"[[:upper:].]{1,}"))
message

##  [1] "C"  "O"  "N"  "G"  "R"  "A"  "T"  "U"  "L"  "AT" "I"  "O"  "N"  "S"  "." 
## [16] "Y"  "O"  "U"  "."  "A"  "R"  "E"  "."  "A"  ".S" "U"  "P"  "E"  "R"  "N" 
## [31] "E"  "R"  "D"

The above process produces a bunch of capital letters, with occassional dots. We’ll build words out of those capital letters.

first_word <- str_c(message[1], message[2], message[3], message[4], message[5], message[6], message[7], message[8], message[9], message[10], message[11], message[12], message[13], message[14])
second_word <- str_c(message[16], message[17], message[18])
third_word <- str_c(message[20], message[21], message[22])
fourth_word <- str_c(message[24])
fifth_word <- str_c(str_replace(message[25], pattern = ".", ""), message[26], message[27], message[28], message[29], message[30], message[31], message[32], message[33])

Created 5 words. Now, I’ll create a complete sentence or phrase out of the five words.

paste(first_word, second_word, third_word, fourth_word, fifth_word)

## [1] "CONGRATULATIONS YOU ARE A SUPERNERD"

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