对于基数R，我们可以使用aggregate + rbind

> aggregate(frequency ~ ., rbind(df1, df2), sum)
  from to frequency
1    a  a         5
2    a  b         7

或者，我们可以使用xtabs + as.data.frame + rbind

> as.data.frame(xtabs(frequency ~ ., rbind(df1, df2)))
  from to Freq
1    a  a    5
2    a  b    7

数据

> dput(df1)
structure(list(from = c("a", "a"), to = c("a", "b"), frequency = 2:3), class = "data.frame", row.names = c(NA,
-2L))

> dput(df2)
structure(list(from = c("a", "a"), to = c("a", "b"), frequency = 3:4), class = "data.frame", row.names = c(NA,
-2L))

一个很酷的（dplyr）选项是使用powerjoin包：

library(powerjoin)
power_left_join(df1, df2, by = c("from", "to"), conflict = `+`)

结果：

from to frequency
1:    a  a         5
2:    a  b         7

df1 <- data.frame(from = c("a", "a"), to = c("a", "b"), frequency = c(2, 3))

df2 <- data.frame(from = c("a", "a"), to = c("a", "b"), frequency = c(3, 4))

# Merge and sum frequencies
merged_df <- bind_rows(df1, df2) %>%
  group_by(from, to) %>%
  summarise(frequency = sum(frequency))

print（merged_df）

from  to    frequency
  <chr> <chr>     <dbl>
1 a     a             5
2 a     b             7

可以使用data.table

library(data.table)
df1 <- data.frame(from = c("a", "a"), to = c("a", "b"), frequency = c(2, 3)) |> setDT()

df2 <- data.frame(from = c("a", "a"), to = c("a", "b"), frequency = c(3, 4)) |> setDT()

df1[df2, on = .(from, to), 
    frequency := x.frequency + i.frequency]

输出

from     to frequency
   <char> <char>     <int>
1:      a      a         5
2:      a      b         7

使用dplyr，我们可以使用两个步骤

df1 <- data.frame(from = c("a", "a"), to = c("a", "b"), frequency = c(2, 3))
df2 <- data.frame(from = c("a", "a"), to = c("a", "b"), frequency = c(3, 4))

inner_join(df1, df2, by = c("to","from")) %>% 
  mutate(frequency = frequency.x + frequency.y)