查找两个数据帧中匹配的两列,并使用 R 将数据帧 2 中的第三列放入数据帧 1 中的新列

Find two columns that match in two dataframes and put third column from dataframe 2 into a new column in dataframe 1 using R

我有 2 个数据框:

df1:
word1 previousWord
a     na
b     a
c     b

另一个数据框看起来像这样

df2: this contains more pairs than exist in df1. It contains every combo possible

word1 previousWord Score
a     a            1
a     b            .5
a     c            .9
b     a            .5
b     b            1
b     c            .2
c     a            .9
c     b            .2
c     c            1

我想在 df2 中找到 df1 中的对(即 b-a、c-b),然后从 df2 中复制分数并将其添加到 df1 中的新列中。

例如,输出如下所示:

word1 previousWord Score
a     na           na
b     a            .5
c     b            .2

这是我尝试过的方法,但它似乎从 df1 中删除了我的很多数据。调换顺序并没有解决这个问题。

df3<-merge(df2, df1, by = c("word1", "previousWord"))

非常感谢任何帮助。

您可以在此处使用 dplyr 中的 left_join()

library(dplyr)
df3<- left_join(df1, df2, by = c("word1", "previousWord"))

输出

  word1 previousWord Score
1     a         <NA>    NA
2     b            a   0.5
3     c            b   0.2

数据

df1 <- structure(list(word1 = c("a", "b", "c"), previousWord = c(NA, 
"a", "b")), class = "data.frame", row.names = c(NA, -3L))

df2 <- structure(list(word1 = c("a", "a", "a", "b", "b", "b", "c", "c", 
"c"), previousWord = c("a", "b", "c", "a", "b", "c", "a", "b", 
"c"), Score = c(1, 0.5, 0.9, 0.5, 1, 0.2, 0.9, 0.2, 1)), class = "data.frame", row.names = c(NA, 
-9L))