如何从与dataframe中其他列的最大值相对应的列中检索值

我有这样一个数据帧：

[,1] [,2] [,3] [,4] [,5] [,6]
 a    1    5     7    9    4
 b    2    8     2    3    5
 c    3    9     2    4    8
 d    4    2     6    1    3

[1] "d" "c" "a" "a" "c"

我想根据其他列的最大值获得列[，1]的值。结果应该是这样的：

[,1] [,2] [,3] [,4] [,5] [,6]
 a    1    5     7    9    4
 b    2    8     2    3    5
 c    3    9     2    4    8
 d    4    2     6    1    3

[1] "d" "c" "a" "a" "c"

---

提前感谢您。

如果您有一个数据帧，您可以使用

which.max

获取每列中的索引最大值，并使用该索引对第一列中的值进行子集

df$V1[sapply(df[-1], which.max)]
#[1] "d" "c" "a" "a" "c"

---

如果您有矩阵（看起来更像），那么由于第一列的原因，所有值都将变成字符，在这种情况下，您可以执行以下操作：

mat[apply(mat[, -1], 2, function(x) which.max(as.numeric(x))), 1]
#[1] "d" "c" "a" "a" "c"

数据

df <- structure(list(V1 = c("a", "b", "c", "d"), V2 = 1:4, V3 = c(5L, 
8L, 9L, 2L), V4 = c(7L, 2L, 2L, 6L), V5 = c(9L, 3L, 4L, 1L), 
V6 = c(4L, 5L, 8L, 3L)), row.names = c(NA, -4L), class = "data.frame")

mat <- structure(c("a", "b", "c", "d", "1", "2", "3", "4", "5", "8", 
"9", "2", "7", "2", "2", "6", "9", "3", "4", "1", "4", "5", "8", 
"3"), .Dim = c(4L, 6L))

df <- structure(list(V1 = c("a", "b", "c", "d"), V2 = 1:4, V3 = c(5L, 
8L, 9L, 2L), V4 = c(7L, 2L, 2L, 6L), V5 = c(9L, 3L, 4L, 1L), 
    V6 = c(4L, 5L, 8L, 3L)), class = "data.frame", row.names = c(NA, 
-4L))

m <- structure(c("a", "b", "c", "d", "1", "2", "3", "4", "5", "8", 
"9", "2", "7", "2", "2", "6", "9", "3", "4", "1", "4", "5", "8", 
"3"), .Dim = c(4L, 6L))

---

df您可以使用
max.col


如果是数据帧
df


如果是矩阵
m

数据

df <- structure(list(V1 = c("a", "b", "c", "d"), V2 = 1:4, V3 = c(5L, 
8L, 9L, 2L), V4 = c(7L, 2L, 2L, 6L), V5 = c(9L, 3L, 4L, 1L), 
V6 = c(4L, 5L, 8L, 3L)), row.names = c(NA, -4L), class = "data.frame")

mat <- structure(c("a", "b", "c", "d", "1", "2", "3", "4", "5", "8", 
"9", "2", "7", "2", "2", "6", "9", "3", "4", "1", "4", "5", "8", 
"3"), .Dim = c(4L, 6L))

df <- structure(list(V1 = c("a", "b", "c", "d"), V2 = 1:4, V3 = c(5L, 
8L, 9L, 2L), V4 = c(7L, 2L, 2L, 6L), V5 = c(9L, 3L, 4L, 1L), 
    V6 = c(4L, 5L, 8L, 3L)), class = "data.frame", row.names = c(NA, 
-4L))

m <- structure(c("a", "b", "c", "d", "1", "2", "3", "4", "5", "8", 
"9", "2", "7", "2", "2", "6", "9", "3", "4", "1", "4", "5", "8", 
"3"), .Dim = c(4L, 6L))

df我们可以重塑为“长”格式，然后
slice
获取第一列的值（假设它是
data.frame

library(dplyr)
library(tidyr)
df %>%
    pivot_longer(cols = -V1) %>%
    group_by(name) %>% 
    slice(which.max(value)) %>% 
    pull(V1)
#[1] "d" "c" "a" "a" "c"

如果是
矩阵
，则使用
as.data.frame
转换为
data.frame

library(dplyr)
library(tidyr)
df %>%
    pivot_longer(cols = -V1) %>%
    group_by(name) %>% 
    slice(which.max(value)) %>% 
    pull(V1)
#[1] "d" "c" "a" "a" "c"

数据
df