Combine two data frames with different number of rows in R

This question already has an answer here:

How to join (merge) data frames (inner, outer, left, right)? 12 answers

---

df1 <- data.frame(wpt = c(1, "meditate", "meditate", 2,3,"meditate"), 
              ID = c(1235, 4562, 0928,6351,3826,0835))
df1$wpt <- as.character(df1$wpt)


df2 <- data.frame(wpt = c(1,2,3), 
              fuel = c(1235, 4562, 0928), 
              distance = c(2,3,4))
df2$wpt <- as.character(df2$wpt)


library(dplyr)
full_join(df1, df2, by = "wpt")

Don't mind the values! You can always rearrange the columns.

       wpt   ID fuel distance
1        1 1235 1235        2
2 meditate 4562   NA       NA
3 meditate  928   NA       NA
4        2 6351 4562        3
5        3 3826  928        4
6 meditate  835   NA       NA

---

Here's a non-merge base R solution built around match() :

link[names(body)[-1L]] <- body[match(link[,1L],body[,1L]),-1L];
link;
##       wpt   ID fuel distance
## 1       1 1235 2221    53927
## 2 mediate 4562   NA       NA
## 3 mediate 0928   NA       NA
## 4       2 6351 4821    48261
## 5       3 3826 8362    47151
## 6 mediate 0835   NA       NA

Data

link <- data.frame(wpt=c('1','mediate','mediate','2','3','mediate'),ID=c('1235','4562','0928'
,'6351','3826','0835'),stringsAsFactors=F);
body <- data.frame(wpt=c(1L,2L,3L),fuel=c(2221L,4821L,8362L),distance=c(53927L,48261L,47151L)
);

---

我认为以下应该工作：

library(data.table)
setkey(link,wpt)
setkey(body,wpt)
merge(link,body,by="wpt",all.x=T)

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