从表对象

Question

我想知道如何从一个表中的特定行R.例如提取一排，

> a <- c(13,13, 
    14,14,14,14,14,14, 
    15,15,15,15,15,15, 
    16,16,16,16,16,16,16,16,16,16,16,16,16,16,16, 
    17,17,17,17,17,17,17, 
    18,18,18,18,18,18,18,18,18,18,18,18,18,18,18,18,18, 
    19,19,19,19,19,19,19,19,19,19,19, 
    20,20,20,20,20,20,20,20,20, 
    21,21,21,21,21,21,21,21,21,21,21, 
    22,22,22,22,22,22,22,22,22, 
    23,23,23,24,25,25,27) 
> table(a) 
a 
13 14 15 16 17 18 19 20 21 22 23 24 25 27 
2 6 6 15 7 17 11 9 11 9 3 1 2 1 

我如何提取表的最后一排？

Answer 1

您的表对象只是一个命名向量。所以，你可以访问的元素通常的方式：

R> b = table(a) 
##To get the numerical values 
R> as.vector(b) 
[1] 2 6 6 15 7 17 11 9 11 9 3 1 2 1 
##To get the names 
R> names(b) 
[1] "13" "14" "15" "16" "17" "18" "19" "20" "21" "22" "23" "24" "25" "27" 

由于b是一个载体，我们只需使用标准分的设置规则：

##Get the last element in the named vector 
R> b[length(b)] 
27 
1 
R> names(b)[length(b)] 
[1] "27"