Question

我正在尝试找到一个可扩展的解决方案来根据另一个data.frame更新data.frame。这是一个最小的例子：

df1 <- data.frame(cbind(c("a","b","b","b","c"),c(1,1,1,2,2),as.numeric(c(0.2,0.6,0.6,0.8,0.4))))
colnames(df1) <- c("ID1", "ID2","Value")

> df1
  ID1 ID2 Value
1   a   1   0.2
2   b   1   0.6
3   b   1   0.6
4   b   2   0.8
5   c   2   0.4

df2 <- data.frame(cbind(2),0,0.45,0.5)
colnames(df2) <- c("ID2", "a","b","c")

> df2
   ID2 a    b    c
1   2  0  0.45  0.5

现在我想通过使用df2值来更新df1的值以获得以下结果：

   ID1 ID2 Value
1   a   1   0.2
2   b   1   0.6
3   b   1   0.6
4   b   2   0.45
5   c   2   0.5

有人可以为此提供帮助吗？

Answer 1

首先，让我们在创建数据集时摆脱cbind，这样它就不会先转换为矩阵并搞乱这些类。

df1 <- data.frame(c("a","b","b","b","c"),c(1,1,1,2,2),c(0.2,0.6,0.6,0.8,0.4))
colnames(df1) <- c("ID1", "ID2","Value")
df2 <- data.frame(2,0,0.45,0.5)
colnames(df2) <- c("ID2", "a","b","c")

然后，我会先将您的第二个数据集转换为长格式，然后就地更新df1

library(data.table) #v>=1.9.6
ldf2 <- melt(setDT(df2), 1)
setDT(df1)[ldf2, Value := i.value, on = c(ID1 = "variable", ID2 = "ID2")]
df1
#    ID1 ID2 Value
# 1:   a   1  0.20
# 2:   b   1  0.60
# 3:   b   1  0.60
# 4:   b   2  0.45
# 5:   c   2  0.50

R基于df2以不同格式更新df1值

1 个答案: