我想使用索引來確定哪些行基於另一個DF的連接來創建新列。使用索引時,我無法執行match()。使用索引替換值
df1 <- data.frame(A=c("A", "C", "E"), B=c(1, 3, 5))
df2 <- data.frame(A=c("A", "C", "E"), C=c("Z", "X", "V"))
idx <- c(1, 3)
df1[match(df1$A, df2$A), "D"] <- df2$C
> df1
A B D
1 A 1 Z
2 C 3 X
3 E 5 V
df1[idx,][match(df1$A, df2$A), "D"] <- df2$C
Warning messages:
1: In `[<-.data.frame`(`*tmp*`, idx, , value = list(A = c(1L, 3L, NA : replacement element 1 has 3 rows to replace 2 rows
# what I would like the outcome to look like
> df1
A B D
1 A 1 Z
2 C 3 NA
3 E 5 V
更新:akrun給了我的想法,首先扔在一個新的列。我現在得到我想要的,但有警告。
df1$D <- NA
df1[idx,][match(df1$A, df2$A), "D"] <- df2$C
Warning messages:
1: In `[<-.data.frame`(`*tmp*`, idx, , value = list(A = c(1L, 3L, NA :
replacement element 1 has 3 rows to replace 2 rows
2: In `[<-.data.frame`(`*tmp*`, idx, , value = list(A = c(1L, 3L, NA :
replacement element 2 has 3 rows to replace 2 rows
3: In `[<-.data.frame`(`*tmp*`, idx, , value = list(A = c(1L, 3L, NA :
replacement element 3 has 3 rows to replace 2 rows
> df1
A B D
1 A 1 3
2 C 3 NA
3 E 5 2
任何解決方案來做到這一點沒有警告?
您可以檢查'DF1 [IDX,]'有隻有兩個行 – akrun
@akrun:感謝您的想法。所以我添加df1 $ D < - NA並運行新代碼。我得到了我想要做的,但是以犧牲警告爲代價。我的意圖是隻包含與索引匹配的數據。 – user2300643
你可以查看'match(df1 $ A,df2 $ A)# [1] 1 2 3'它匹配所有行 – akrun