循環(huán)對(duì)于代碼運(yùn)行來(lái)說(shuō)是非常消耗時(shí)間和資源的衣摩，在R中翼抠，要盡量少使用for while循環(huán)，用apply函數(shù)族的話對(duì)于數(shù)據(jù)處理會(huì)十分方便苞慢。
apply {base}
通過(guò)對(duì)數(shù)組或者矩陣的一個(gè)維度使用函數(shù)生成值得列表或者數(shù)組、向量英妓。
apply(X, MARGIN, FUN, ...)
X 陣列挽放，包括矩陣
MARGIN 1表示矩陣行，2表示矩陣列蔓纠，也可以是c(1,2)
例：
xxx<-matrix(1:20,ncol=4)
apply(xxx,1,mean)
[1] 8.5 9.5 10.5 11.5 12.5
apply(xxx,2,mean)
[1] 3 8 13 18
xxx
[,1] [,2] [,3] [,4]
[1,] 1 6 11 16
[2,] 2 7 12 17
[3,] 3 8 13 18
[4,] 4 9 14 19
[5,] 5 10 15 20
lapply {base}
通過(guò)對(duì)x的每一個(gè)元素運(yùn)用函數(shù)辑畦，生成一個(gè)與元素個(gè)數(shù)相同的值列表
lapply(X, FUN, ...)
X表示一個(gè)向量或者表達(dá)式對(duì)象，其余對(duì)象將被通過(guò)as.list強(qiáng)制轉(zhuǎn)換為list
例：
x <- list(a = 1:10, beta = exp(-3:3), logic = c(TRUE,FALSE,FALSE,TRUE))
x
$a
[1] 1 2 3 4 5 6 7 8 9 10
$beta
[1] 0.04978707 0.13533528 0.36787944 1.00000000 2.71828183 7.38905610
[7] 20.08553692
$logic
[1] TRUE FALSE FALSE TRUE
lapply(x,mean)
$a
[1] 5.5
$beta
[1] 4.535125
$logic
[1] 0.5
sapply {base}
這是一個(gè)用戶友好版本腿倚，是lapply函數(shù)的包裝版纯出。該函數(shù)返回值為向量、矩陣敷燎，如果simplify=”array”暂筝，且合適的情況下，將會(huì)通過(guò)simplify2array()函數(shù)轉(zhuǎn)換為陣列懈叹。sapply(x, f, simplify=FALSE, USE.NAMES=FALSE)返回的值與lapply(x,f)是一致的乖杠。
sapply(X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE)
X表示一個(gè)向量或者表達(dá)式對(duì)象，其余對(duì)象將被通過(guò)as.list強(qiáng)制轉(zhuǎn)換為list
simplify 邏輯值或者字符串澄成，如果可以胧洒，結(jié)果應(yīng)該被簡(jiǎn)化為向量、矩陣或者高維數(shù)組墨状。必須是命名的卫漫，不能是簡(jiǎn)寫(xiě)。默認(rèn)值是TRUE肾砂，若合適將會(huì)返回一個(gè)向量或者矩陣列赎。如果simplify=”array”，結(jié)果將返回一個(gè)陣列镐确。
USE.NAMES 邏輯值包吝，如果為T(mén)RUE饼煞，且x沒(méi)有被命名，則對(duì)x進(jìn)行命名诗越。
例：
sapply(k, paste,USE.NAMES=FALSE,1:5,sep="...")
[,1] [,2] [,3]
[1,] "a...1" "b...1" "c...1"
[2,] "a...2" "b...2" "c...2"
[3,] "a...3" "b...3" "c...3"
[4,] "a...4" "b...4" "c...4"
[5,] "a...5" "b...5" "c...5"
sapply(k, paste,USE.NAMES=TRUE,1:5,sep="...")
a b c
[1,] "a...1" "b...1" "c...1"
[2,] "a...2" "b...2" "c...2"
[3,] "a...3" "b...3" "c...3"
[4,] "a...4" "b...4" "c...4"
[5,] "a...5" "b...5" "c...5"
sapply(k, paste,USE.NAMES=TRUE,1:5,sep="...",simplyfy=TRUE)
a b c
[1,] "a...1...TRUE" "b...1...TRUE" "c...1...TRUE"
[2,] "a...2...TRUE" "b...2...TRUE" "c...2...TRUE"
[3,] "a...3...TRUE" "b...3...TRUE" "c...3...TRUE"
[4,] "a...4...TRUE" "b...4...TRUE" "c...4...TRUE"
[5,] "a...5...TRUE" "b...5...TRUE" "c...5...TRUE"
sapply(k, paste,simplify=TRUE,USE.NAMES=TRUE,1:5,sep="...")
a b c
[1,] "a...1" "b...1" "c...1"
[2,] "a...2" "b...2" "c...2"
[3,] "a...3" "b...3" "c...3"
[4,] "a...4" "b...4" "c...4"
[5,] "a...5" "b...5" "c...5"
sapply(k, paste,simplify=FALSE,USE.NAMES=TRUE,1:5,sep="...")
$a
[1] "a...1" "a...2" "a...3" "a...4" "a...5"
$b
[1] "b...1" "b...2" "b...3" "b...4" "b...5"
$c
[1] "c...1" "c...2" "c...3" "c...4" "c...5"
vapply {base}
vapply類似于sapply函數(shù)砖瞧，但是它的返回值有預(yù)定義類型，所以它使用起來(lái)會(huì)更加安全嚷狞，有的時(shí)候會(huì)更快
在vapply函數(shù)中總是會(huì)進(jìn)行簡(jiǎn)化块促，vapply會(huì)檢測(cè)FUN的所有值是否與FUN.VALUE兼容，以使他們具有相同的長(zhǎng)度和類型床未。類型順序：邏輯<</span>整型<</span>實(shí)數(shù)<</span>復(fù)數(shù)
vapply(X, FUN, FUN.VALUE, ..., USE.NAMES = TRUE)
X表示一個(gè)向量或者表達(dá)式對(duì)象竭翠，其余對(duì)象將被通過(guò)as.list強(qiáng)制轉(zhuǎn)換為list
simplify 邏輯值或者字符串，如果可以薇搁，結(jié)果應(yīng)該被簡(jiǎn)化為向量斋扰、矩陣或者高維數(shù)組。必須是命名的只酥，不能是簡(jiǎn)寫(xiě)褥实。默認(rèn)值是TRUE，若合適將會(huì)返回一個(gè)向量或者矩陣裂允。如果simplify=”array”，結(jié)果將返回一個(gè)陣列哥艇。
USE.NAMES 邏輯值绝编，如果為T(mén)RUE，且x沒(méi)有被命名貌踏，則對(duì)x進(jìn)行命名十饥。
FUN.VALUE 一個(gè)通用型向量，F(xiàn)UN函數(shù)返回值得模板
例：
x<-data.frame(a=rnorm(4,4,4),b=rnorm(4,5,3),c=rnorm(4,5,3))
vapply(x,mean,c(c=0))
a b c
1.8329043 6.0442858 -0.1437202
k<-function(x)
- {
- list(mean(x),sd(x))
- }
vapply(x,k,c(c=0))
錯(cuò)誤于vapply(x, k, c(c = 0)) : 值的長(zhǎng)度必需為1祖乳，
但FUN(X[[1]])結(jié)果的長(zhǎng)度卻是2
vapply(x,k,c(c=0,b=0))
錯(cuò)誤于vapply(x, k, c(c = 0, b = 0)) : 值的種類必需是'double'逗堵，
但FUN(X[[1]])結(jié)果的種類卻是'list'
vapply(x,k,c(list(c=0,b=0)))
a b c
c 1.832904 6.044286 -0.1437202
b 1.257834 1.940433 3.649194
tapply {base}
對(duì)不規(guī)則陣列使用向量，即對(duì)一組非空值按照一組確定因子進(jìn)行相應(yīng)計(jì)算
tapply(X, INDEX, FUN, ..., simplify = TRUE)
x 一個(gè)原子向量眷昆，典型的是一個(gè)向量
INDEX 因子列表蜒秤，和x長(zhǎng)度一樣，元素將被通過(guò)as.factor強(qiáng)制轉(zhuǎn)換為因子
simplify 若為FALSE亚斋，tapply將以列表形式返回陣列作媚。若為T(mén)RUE，F(xiàn)UN則直接返回?cái)?shù)值
例：
height <- c(174, 165, 180, 171, 160)
sex<-c("F","F","M","F","M")
tapply(height, sex, mean)
F M
170 170
eapply {base}
eapply函數(shù)通過(guò)對(duì)environment中命名值進(jìn)行FUN計(jì)算后返回一個(gè)列表值帅刊，用戶可以請(qǐng)求所有使用過(guò)的命名對(duì)象纸泡。
eapply(env, FUN, ..., all.names = FALSE, USE.NAMES = TRUE)
env 將被使用的環(huán)境
all.names 邏輯值，指示是否對(duì)所有值使用該函數(shù)
USE.NAMES 邏輯值赖瞒，指示返回的列表結(jié)果是否包含命名
例：
require(stats)env <- new.env(hash = FALSE) # so the order is fixed
env$a <- 1:10
env$beta <- exp(-3:3)
env$logic <- c(TRUE, FALSE, FALSE, TRUE)what have we there?
utils::ls.str(env)
a : int [1:10] 1 2 3 4 5 6 7 8 9 10
beta : num [1:7] 0.0498 0.1353 0.3679 1 2.7183 ...
logic : logi [1:4] TRUE FALSE FALSE TRUEcompute the mean for each list element
eapply(env, mean)
$logic
[1] 0.5
$beta
[1] 4.535125
$a
[1] 5.5
unlist(eapply(env, mean, USE.NAMES = FALSE))
[1] 0.500000 4.535125 5.500000median and quartiles for each element (making use of "..." passing):
eapply(env, quantile, probs = 1:3/4)
$logic
25% 50% 75%
0.0 0.5 1.0
$beta
25% 50% 75%
0.2516074 1.0000000 5.0536690
$a
25% 50% 75%
3.25 5.50 7.75
eapply(env, quantile)
$logic
0% 25% 50% 75% 100%
0.0 0.0 0.5 1.0 1.0
$beta
0% 25% 50% 75% 100%
0.04978707 0.25160736 1.00000000 5.05366896 20.08553692
$a
0% 25% 50% 75% 100%
1.00 3.25 5.50 7.75 10.00
mapply {base}
mapply是sapply的多變量版本女揭。將對(duì)...中的每個(gè)參數(shù)運(yùn)行FUN函數(shù)蚤假，如有必要，參數(shù)將被循環(huán)吧兔。
mapply(FUN, ..., MoreArgs = NULL, SIMPLIFY = TRUE, USE.NAMES = TRUE)
MoreArgs FUN函數(shù)的其他參數(shù)列表
SIMPLIFY 邏輯或者字符串勤哗，可以減少結(jié)果成為一個(gè)向量、矩陣或者更高維陣列掩驱，詳見(jiàn)sapply的simplify參數(shù)
USE.NAMES 邏輯值芒划，如果第一個(gè)參數(shù)...已被命名，將使用這個(gè)字符向量作為名字
例：
mapply(rep, 1:4, 4:1)
[[1]]
[1] 1 1 1 1
[[2]]
[1] 2 2 2
[[3]]
[1] 3 3
[[4]]
[1] 4
rapply {base}
rapply是lapply的遞歸版本
rapply(X, FUN, classes = "ANY", deflt = NULL, how = c("unlist", "replace", "list"), ...)
X 一個(gè)列表
classes 關(guān)于類名的字符向量欧穴，或者為any時(shí)則匹配任何類
deflt 默認(rèn)結(jié)果民逼，如果使用了how=”replace”，則不能使用
how 字符串匹配三種可能結(jié)果
apply.png
