如何找到每行的2个最大值，然后将它们加在一起？

您可以进行按行计算，对指定列中的值进行排序，然后将最高的两个值相加：

library(dplyr)

df <- data.frame(Mon = c(12,15,42,43,56,73,23),
                 Tues = c(15,14,12,75,98,79,68),
                 Wed = c(13,42,35,64,35,95,56),
                 Thur = c(23,46,32,94,78,68,35),
                 Friday = c(25,23,64,35,27,54,32))



df %>% 
  rowwise() %>% 
  mutate(two_max = sum(sort(c(Mon, Tues, Wed, Thur, Friday), decreasing = TRUE)[1:2])) %>% 
  ungroup()

如果您不想手动指定列名，也可以一次选择所有数字列：

df %>% 
  rowwise() %>% 
  mutate(two_max = sum(sort(c_across(where(is.numeric)), decreasing = TRUE)[1:2])) %>% 
  ungroup()

两种策略都能得出结果：

# A tibble: 7 x 6
    Mon  Tues   Wed  Thur Friday two_max
  <dbl> <dbl> <dbl> <dbl>  <dbl>   <dbl>
1    12    15    13    23     25      48
2    15    14    42    46     23      88
3    42    12    35    32     64     106
4    43    75    64    94     35     169
5    56    98    35    78     27     176
6    73    79    95    68     54     174
7    23    68    56    35     32     124