Week 3 Strings and Regex

Get some data about college majors, from fivethirtyeight.com’s Github

dataURL <- "https://raw.githubusercontent.com/fivethirtyeight/data/master/college-majors/majors-list.csv"
majors <- read.csv(url(dataURL))
majors <- majors$Major
majors[1:11]

##  [1] "GENERAL AGRICULTURE"                  
##  [2] "AGRICULTURE PRODUCTION AND MANAGEMENT"
##  [3] "AGRICULTURAL ECONOMICS"               
##  [4] "ANIMAL SCIENCES"                      
##  [5] "FOOD SCIENCE"                         
##  [6] "PLANT SCIENCE AND AGRONOMY"           
##  [7] "SOIL SCIENCE"                         
##  [8] "MISCELLANEOUS AGRICULTURE"            
##  [9] "FORESTRY"                             
## [10] "NATURAL RESOURCES MANAGEMENT"         
## [11] "FINE ARTS"

Identify the majors that contain either “DATA” or “STATISTICS”

majors[str_detect(majors, "DATA|STATISTICS")]

## [1] "MANAGEMENT INFORMATION SYSTEMS AND STATISTICS"
## [2] "COMPUTER PROGRAMMING AND DATA PROCESSING"     
## [3] "STATISTICS AND DECISION SCIENCE"

———————————————–

Practice manipulating strings with regex in R

fruitvec <- c("bell pepper", "bilberry", "blackberry", "blood orange",
              "blueberry", "cantaloupe", "chili pepper", "cloudberry",
              "elderberry", "lime", "lychee", "mulberry", "olive",
              "salal berry")
fruitvec

##  [1] "bell pepper"  "bilberry"     "blackberry"   "blood orange" "blueberry"   
##  [6] "cantaloupe"   "chili pepper" "cloudberry"   "elderberry"   "lime"        
## [11] "lychee"       "mulberry"     "olive"        "salal berry"

Now the task is to create a string representation of fruitvec:

strfruitvec <- str_flatten(fruitvec, collapse = '", "')
cat(c('c("', strfruitvec, '")'), sep = '')

## c("bell pepper", "bilberry", "blackberry", "blood orange", "blueberry", "cantaloupe", "chili pepper", "cloudberry", "elderberry", "lime", "lychee", "mulberry", "olive", "salal berry")

So the cat function produces the desired output format, but in order to produce an actual object that is a string and includes double quotes around each item, I don’t know if that’s possible, without backslashes appearing in the object.

stringy_vec <- function(charvec) {
  flat <- str_flatten(charvec, collapse = '", "')
  cat(c('c("', flat, '")'), sep = '')
}
cheeses <- c('gouda', 'brie', 'stilton', 'american', 'string cheese')
stringy_vec(cheeses)

## c("gouda", "brie", "stilton", "american", "string cheese")

—————————————————-

Describe, in words, what these expressions will match:

(.)\1\1

A character that occurs 3 times in a row

"(.)(.)\\2\\1"

A palindromic series of 4 characters, like “anna” or “zzzz”

(..)\1

Four characters where 3 and 4 are the same as 1 and 2, like “yoyo”

"(.).\\1.\\1"

A 5-char sequence where chars 1, 3, and 5 are the same, like “orono”

"(.)(.)(.).*\\3\\2\\1"

A series of at least 6 chars, ending with the same 3 it started with,

but in reversed order, like “redder” or “madam, i’m adam”

————————————————–

Construct regular expressions to match words that:

–Start and end with the same character.

"\\b(.)\\S*\\1\\b" allows internal numbers and symbols, so it

matches “pop-up” and “s#$%s”, e.g.

–Contain a repeated pair of letters (e.g. “church” contains “ch” repeated twice.)

"\\b.*([a-zA-Z][a-zA-Z])[a-zA-Z-]*\\1[a-zA-Z]*\\b" allows only letters,

plus hyphens between the repeated pairs, so it matches ‘mai-tai’

but only the “yoyo” part of “yoyo-lover”, e.g.

–Contain one letter repeated in at least three places (e.g. “eleven” contains three “e”s.)

"\\b[a-zA-Z]*([a-zA-Z])[a-zA-Z]+\\1[a-zA-Z]+\\1[a-zA-Z]*\\b"

…