Question

鉴于此表

df <- data.frame(col1 = c(letters[3:5], "b","a"),
                 col2 = c(2:3, 1,1,1))

如何判断R返回＆＃34; a＆＃34;。这意味着，从值为1的三个字符（最低值的平局），我想只按字母顺序选择第一个

Answer 1

尝试：

> min(as.character(df[df$col2==min(df$col2),1]))
[1] "a"

解释：

# first find col1 list in rows with minimum of df$col2
> xx = df[df$col2==min(df$col2),1]
> xx
[1] e b a
Levels: a b c d e

# Now find the minimum amongst these after converting factor to character: 
> min(as.character(xx))
[1] "a"
>

Answer 2

我想你想要order

with(df, col1[order(col2, col1)][1])
# [1] a
# Levels: a b c d e

或

as.character(with(df, col1[order(col2, col1)][1]))
# [1] "a"

您可以使用

按第2列中的有序值对第1列进行排序

df[with(df, order(col2, col1)),]
#   col1 col2
# 5    a    1
# 4    b    1
# 3    e    1
# 1    c    2
# 2    d    3

排序领带的元素

2 个答案: