Data 607_Week 3 HW_ER

Week 3 Excercise 1

Filtering a data frame:

df <- read.csv('https://raw.githubusercontent.com/fivethirtyeight/data/master/college-majors/majors-list.csv')

df %>% 
  filter(str_detect(Major, "DATA|STATISTICS"))

##   FOD1P                                         Major          Major_Category
## 1  6212 MANAGEMENT INFORMATION SYSTEMS AND STATISTICS                Business
## 2  2101      COMPUTER PROGRAMMING AND DATA PROCESSING Computers & Mathematics
## 3  3702               STATISTICS AND DECISION SCIENCE Computers & Mathematics

Week 3 Excercise 2

Combining a string:

str_c(c("bell pepper","bilberry","blackberry","blood orange","blueberry","cantaloupe","chili pepper","cloudberry", "olive","salal berry"), collapse=", ")

## [1] "bell pepper, bilberry, blackberry, blood orange, blueberry, cantaloupe, chili pepper, cloudberry, olive, salal berry"

Week 3 Excercise 3

Describe the following expressions in words:

• (.)\1\1
  

  One character followed by 2 matching characters

• “(.)(.)\\2\\1”
  

  Double back slash indicates for use with str_view. Two single character group followed by matching of 2nd group letter followed by last character matching the 1st

• (..)\1
  

  Two character group followed by identical two character.

• “(.).\\1.\\1”
  

  Double back slash indicates for use with str_view. One single character group, followed any character followed by 1st group letter follow by any letter followed by first group letter.

• "(.)(.)(.).*\\3\\2\\1"
  

  Double back slash indicates for use with str_view. Three single character groups followed by any character followed by matching of third group letter followed bye 2nd group letter followed by 1st group letter.

Week 3 Excercise 4

Construct regular expressions to match words that:

• Start and end with the same character.
  

  (.).*\1

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

  (..).*\1

• Contain one letter repeated in at least three places eleven" contains three “e”s.)
  

  (.).*\1.*\1