String and Regular expressions

Question 1

[1] “base” “boot” “class” “cluster” “codetools”

to

chr [1:31] “base” “boot” “class” “cluster” “codetools” …

Answer 1

pkgs = gsub(“([^"]+)"([a-zA-Z0-9\.]+)"”, “\2 “, pkgs)

pkgs = unlist(strsplit(pkgs, “[[:space:]]+”))

Question 2

OR

Answer 2

I

Question 3

any word

Answer 3

.*

Question 4

gsub()/sub()

gregexpr()/regexpr()

Answer 4

greedy/not-gready

Question 5

space

Answer 5

[:space:]

Question 6

Empty space between characters

Answer 6

\W

Question 7

words = unlist(strsplit(gpl, “\W”))

words = words[words != “”]

Answer 7

把文本拆成单词

Question 8

tail(sort(table(tolower(words))), 10)

Answer 8

统计词频 # 频数最大的10个单词

Question 9

paste(1:3, “a”)

Answer 9

[1] “1 a” “2 a” “3 a”

Question 10

paste(1:3, “a”, sep = “-“)

Answer 10

[1] “1-a” “2-a” “3-a”

Question 11

paste(letters[1:10], collapse = “~”)

Answer 11

[1] “a~b~c~d~e~f~g~h~i~j”

Question 12

paste(1:3, “a”, sep = “-“, collapse = “+”)

Answer 12

[1] “1-a+2-a+3-a”

Question 13

gsub(“.”, “=”, “a.b.c”)

Answer 13

[1] “=====”

Question 14

gsub(“\.”, “=”, “a.b.c”)

Answer 14

[1] “a=b=c”