R 기초; 반복 적용 - Apply Family

R 기초; 반복 적용 - Apply Family

 

apply()

lapply()

sapply()

mapply()

 

?apply

 

x <- matrix(1:20, 4, 5)

x

     [,1] [,2] [,3] [,4] [,5]
[1,]    1    5    9   13   17
[2,]    2    6   10   14   18
[3,]    3    7   11   15   19
[4,]    4    8   12   16   20

 

apply(X=x, MARGIN=1, FUN=max)

[1] 17 18 19 20

 

apply(X=x, MARGIN=2, FUN=min)

[1]  1  5  9 13 17

 

y <- array(1:24, c(4, 3, 2))

, , 1

     [,1] [,2] [,3]
[1,]    1    5    9
[2,]    2    6   10
[3,]    3    7   11
[4,]    4    8   12

, , 2

     [,1] [,2] [,3]
[1,]   13   17   21
[2,]   14   18   22
[3,]   15   19   23
[4,]   16   20   24

 

 

apply(y, 1, paste, collapse=",")

[1] "1,5,9,13,17,21"  "2,6,10,14,18,22" "3,7,11,15,19,23" "4,8,12,16,20,24"

 

 

a <- c(1, 5, 9, 13, 17, 21)

a

[1]  1  5  9 13 17 21

 

paste(a)

[1] "1"  "5"  "9"  "13" "17" "21"

 

paste(a, collapse=",")

[1] "1,5,9,13,17,21"

 

apply(y, 2, paste, collapse=",")

[1] "1,2,3,4,13,14,15,16"    "5,6,7,8,17,18,19,20"    "9,10,11,12,21,22,23,24"

 

apply(y, 3, paste, collapse=",")

[1] "1,2,3,4,5,6,7,8,9,10,11,12"          "13,14,15,16,17,18,19,20,21,22,23,24"

 

 

apply(y, c(1, 2), paste, collapse=",")

     [,1]   [,2]   [,3]   
[1,] "1,13" "5,17" "9,21" 
[2,] "2,14" "6,18" "10,22"
[3,] "3,15" "7,19" "11,23"
[4,] "4,16" "8,20" "12,24"

 

# 타이타닉 호 침몰 사건 데이터 불러오기

Titanic

 

# 데이터 구조 확인하기 str()

str(Titanic)

 

apply(Titanic, 1, sum)

 1st  2nd  3rd Crew 
 325  285  706  885 

 

apply(Titanic, 4, sum)

  No  Yes 
1490  711 

 

apply(Titanic, "Class", sum)

 1st  2nd  3rd Crew 
 325  285  706  885 

 

apply(Titanic, c(1, 4), sum)

      Survived
Class   No Yes
  1st  122 203
  2nd  167 118
  3rd  528 178
  Crew 673 212

 

 

lapply()

sapply()

 

# 연도별 시험점수 데이터 생성하기

exams <- list(s20=c(78,89,91,85,95,98), s21=c(85,86,97,99,90), s22=c(98,96,89,90,93,85,92), s23=c(98,96,91,88,93,99))

exams

$s20
[1] 78 89 91 85 95 98

$s21
[1] 85 86 97 99 90

$s22
[1] 98 96 89 90 93 85 92

$s23
[1] 98 96 91 88 93 99

 

 

# 연도별 학생수 알아보기

lapply(exams, length)

$s20
[1] 6

$s21
[1] 5

$s22
[1] 7

$s23
[1] 6

 

# 연도별 학생수

sapply(exams, length)

s20 s21 s22 s23 
  6   5   7   6 

 

# 연도별 평균

sapply(exams, mean)

     s20      s21      s22      s23 
89.33333 91.40000 91.85714 94.16667 

 

 

# 연도별 표준편차

sapply(exams, sd)

     s20      s21      s22      s23 
7.174027 6.348228 4.375255 4.262237 

 

sapply(exams, range)

     s20 s21 s22 s23
[1,]  78  85  85  88
[2,]  98  99  98  99

 

 

 

head(iris)

lapply(iris, class)

sapply(iris, class)

 

sapply(iris, mean)

 

sapply(iris, function(x), ifelse(is.numeric(x), mean(x), NA))

 

mapply(rep, 1:4, 4:1)

rep(1,4)

rep(2,3)

rep(3,2)

rep(4,1)

 

mapply(rep, 1:4, 4:1)