R:根据来自另一个数据框的匹配行更新列 [英] R: Update column based on matching rows from another data frame

问题描述

我有

mydf1 <- data.frame(ID = c(1,2,3,4,5), color = c("red", NA, NA, NA, "green"), name = c("tom", "dick", "harry", "steve", "mike"))
mydf2 <- data.frame(ID = c(1,2,99), color = c("red", "orange", "yellow"), name = c("tom", "dick", "Aaron"))

对于任何ID和名称都匹配的行，我想用mydf2中的相应颜色更新mydf1 $ color.所需的输出将是将第2行中的颜色更新为橙色，而其余颜色保持不变:

I would like to update mydf1$color with the corresponding color from mydf2 for any rows that match on both ID and name. The desired output would be to update the color in row 2 to orange and leave the rest as is:

   ID  color   name
1  1   red     tom
2  2   orange  dick
3  3   <NA>    harry
4  4   <NA>    steve
5  5   green   mike

我尝试了非对称合并的解决方案，如先前的文章中所述，但是在mydf1中获得了我某些字段的不希望有的覆盖.然后，我尝试按照另一篇文章中的建议使用match，但是收到错误消息.不知道为什么匹配条件不起作用.

I tried solutions with asymmetric merging as in some previous posts, but obtained undesired overwriting of some of my fields in mydf1. I then tried using match as suggested in another post but received an error. Not sure why the match condition is not working.

mydf1$color <- mydf2$color[match(mydf1[c("ID", "name")], mydf2[c("ID", "name")])]

推荐答案

我们可以在和'name'列上使用 data.table 上的连接.并通过赋值(:= )

library(data.table)
setDT(mydf1)[mydf2, color := i.color, on = .(ID, name)]
mydf1
#   ID  color  name
#1:  1    red   tom
#2:  2 orange  dick
#3:  3   <NA> harry
#4:  4   <NA> steve
#5:  5  green  mike

---

match 适用于 vector/matrix ，不适用于 data.frame .如果需要使用 match ，则粘贴每个数据集中的'ID'，'name'并进行 match

---

match works on vector/matrix and not on data.frame. If we need to use match, then paste the 'ID', 'name' from each datasets and do a match

i1 <- match(paste(mydf1$ID, mydf1$name), paste(mydf2$ID, mydf2$name), nomatch = 0)

---

或使用 tidyverse

library(dplyr)
mydf1 %>%
   left_join(mydf2, by = c("ID", "name")) %>%
    transmute(ID, name, color = coalesce(as.character(color.x), 
                                         as.character(color.y)))
#  ID  name  color
#1  1   tom    red
#2  2  dick orange
#3  3 harry   <NA>
#4  4 steve   <NA>
#5  5  mike  green

这篇关于R:根据来自另一个数据框的匹配行更新列的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！