通过匹配两个数据框中的每一行中的值来填充列值

Question

It's a little bit hard to describe my problem. Suppose I have two data.frame and I have to fill column values by matching values in each row.

data1
         date  lat   long      ele  
1 16-JAN-1995 36.2 -113.8       NA
2 16-JAN-1995 33.8 -113.8       NA
3 16-JAN-1995 31.2 -113.8       NA
4 16-JAN-1995 28.8 -113.8       NA
5 16-JAN-1995 26.2 -113.8       NA
6 16-JAN-1995 23.8 -113.8       NA

data2
   lat   long     ele
1 36.2 -113.8 1526.25
2 33.8 -113.8  612.94
3 31.2 -113.8  328.62
4 28.8 -113.8  367.81
5 26.2 -113.8   58.50
6 23.8 -113.8    0.00

Data1 has around 40k rows, and data2 has around 500.

I want

if data1$lat == data2$lat and data1$long == data2$long , then data1$ele == data2$ele .

I also want to check the lat and long values row by row of the 2 dataframes to ensure the long&lat value matches.

I have tried using data.table() and merge(), but none of them seems to be working... Any ideas?

Answer 1

Simple solution in base R:

indices <- df1$lat == df2$lat & df1$long == df2$long

df1$ele[indices] <- df2$ele[indices]

Answer 2

Another way to go about it, via @Roman Lustrik's suggestion to concatenate. Also in base R.

df1$ele <- df2[match(paste(df1$lat,df1$long),paste(df2$lat,df2$long)),"ele"]