R：當 max <= min 時，如何替換（切換）數據幀中一行中的最大值和最小值？

Question

僅當 max <= min 時，我們如何才能替換（切換）此數據幀中每一行的最大值和最小值？

> my_data

   year month day   max      min
1  2019     1   1   20.4   -24.4
2  2019     1   2   12.9   -20.4
3  2019     1   3  -27.1    10.3
4  2019     1   4  -20.8    11.0
5  2019     1   5  -16.2    -8.9

結果應該是這樣的：

> my_data

   year month day   max      min
1  2019     1   1   20.4   -24.4
2  2019     1   2   12.9   -20.4
3  2019     1   3   10.3   -27.1
4  2019     1   4   11.0   -20.8
5  2019     1   5   -8.9   -16.2

提前致謝。

Answer 1

一種選擇是pmax/pmin

library(dplyr)
my_data %>% 
    mutate(maxnew =  pmax(max, min), minnew = pmin(max, min))  %>%
    select(year, month, day, max = maxnew, min = minnew)
#  year month day  max   min
#1 2019     1   1 20.4 -24.4
#2 2019     1   2 12.9 -20.4
#3 2019     1   3 10.3 -27.1
#4 2019     1   4 11.0 -20.8
#5 2019     1   5 -8.9 -16.2

---

或者一種緊湊的方式是使用base R

nm1 <- c('max', 'min')
my_data[nm1] <- t(apply(my_data[nm1], 1, sort))[, 2:1]

---

或使用pmax/pmin

my_data[nm1] <- lapply(list(pmax, pmin), function(f) do.call(f, my_data[nm1]))

數據

my_data <- structure(list(year = c(2019L, 2019L, 2019L, 2019L, 2019L), month = c(1L, 
1L, 1L, 1L, 1L), day = 1:5, max = c(20.4, 12.9, -27.1, -20.8, 
-16.2), min = c(-24.4, -20.4, 10.3, 11, -8.9)), 
class = "data.frame", row.names = c("1", 
"2", "3", "4", "5"))

Answer 2

我們可以找到max小於min的索引。 將這些max存儲在臨時變量中，然后使用它交換最大值和最小值。

inds <- df$max < df$min
temp <- df$max[inds]
df$max[inds] <- df$min[inds]
df$min[inds] <- temp
df

#  year month day  max   min
#1 2019     1   1 20.4 -24.4
#2 2019     1   2 12.9 -20.4
#3 2019     1   3 10.3 -27.1
#4 2019     1   4 11.0 -20.8
#5 2019     1   5 -8.9 -16.2

數據

df <- structure(list(year = c(2019L, 2019L, 2019L, 2019L, 2019L), month = c(1L, 
1L, 1L, 1L, 1L), day = 1:5, max = c(20.4, 12.9, -27.1, -20.8, 
-16.2), min = c(-24.4, -20.4, 10.3, 11, -8.9)), class = "data.frame", 
row.names = c("1", "2", "3", "4", "5"))