5、数据框dataframe data.frame
创建
data.frame()
1 > a<-c(1,2,3,4,5) 2 > b<-c('a','b','c','d','e') 3 > c<-c(T,F,F,F,T) 4 > x<-data.frame(a,b,c) 5 > x 6 a b c 7 1 1 a TRUE 8 2 2 b FALSE 9 3 3 c FALSE 10 4 4 d FALSE 11 5 5 e TRUE
PS:子元素个数不同时会报错
1 > a<-c(1,2,3,4,5,6,7) 2 > b<-c('a','b','c','d','e') 3 > c<-c(T,F,F,F,T) 4 > x<-data.frame(a,b,c) 5 Error in data.frame(a, b, c) : 参数值意味着不同的行数: 7, 5
PS：dataframe与其他语言中的dataset数据集类似
数据引用
1 > x[c('a','c')] 2 a c 3 1 1 TRUE 4 2 2 FALSE 5 3 3 FALSE 6 4 4 FALSE 7 5 5 TRUE 8 > x[2:3] 9 b c 10 1 a TRUE 11 2 b FALSE 12 3 c FALSE 13 4 d FALSE 14 5 e TRUE 15 > x[2:3,2] 16 [1] b c 17 Levels: a b c d e 18 > x[2:3,1] 19 [1] 2 3 20 > x[2:3,3] 21 [1] FALSE FALSE
PS：$引用法
1 > x$a 2 [1] 1 2 3 4 5
attach（）与detach()
1 > attach(x) 2 The following objects are masked _by_ .GlobalEnv: 3 4 a, b, c 5 6 > a 7 [1] 1 2 3 4 5 6 7 8 > b 9 [1] "a" "b" "c" "d" "e" 10 > c 11 [1] TRUE FALSE FALSE FALSE TRUE 12 > a[5] 13 [1] 5 14 > b[3] 15 [1] "c" 16 > detach(x) 17 > a 18 [1] 1 2 3 4 5 6 7 19 > b 20 [1] "a" "b" "c" "d" "e" 21 > c 22 [1] TRUE FALSE FALSE FALSE TRUE 23 > remove(a,b) 24 > remove(c) 25 > a 26 Error: object 'a' not found 27 > b 28 Error: object 'b' not found 29 > attach(x) 30 > a 31 [1] 1 2 3 4 5 32 > b 33 [1] a b c d e 34 Levels: a b c d e 35 > detach(x)
with()
1 > with(x,{ 2 + m<-a[1]+a[5] 3 + m 4 + n<-paste(b[1],b[2],b[5],sep = '+') 5 + n 6 + }) 7 [1] "a+b+e"
Usage
data.frame(..., row.names = NULL, check.rows = FALSE,
check.names = TRUE, fix.empty.names = TRUE,
stringsAsFactors = default.stringsAsFactors())