Check if a value in a df exist in another dataframe and add column

Question

Both fairly large For example :

Df1

Name name2  code2 code3
A    1      2     3
B    1      2     3
C    1      2     3

Df2

Name      lat           lon
A         5             6
C         1             2

I want to compare df1 with df2, If match add in the (lat lon) col to df1

Df1

Name name 2 code2 code3  lat    lon
A    1     2     3      5      6
B    1     2     3
C    1     2     3      1      2

I have tried

test <- merge(df1, df2, by = 'Name', all = TRUE)

However it said that column names 'name' 'name1' are duplicated in the result. ( please assume that changing the column name is not an option )

I also tried a for loop

For( i in 1: nrow(df1)) {
      If ( df1$`Name`[I] %in% df2$Name) {
            Df1$lat[I] = df2$lat 
      }
}

However I do not know how to get the matched lat and lon to add to df1. Any help? Thanks

I have a column with a similar name so it still gives me the error that column names are duplicated in the result — Plle02, Dec 06 '16 at 08:37
`library(dplyr)` and left join the two table `left_join(Df1, Df2)` — dimitris_ps, Dec 06 '16 at 08:39
`merge(df1, df2, by = "Name", all.x = TRUE)` works fine, make the problem reproducible. — zx8754, Dec 06 '16 at 08:50

score 0 · Answer 1 · answered Dec 06 '16 at 09:04

0

Try something like this:

merge(df1, df2, by.x = 'Name1',by.y = 'Name', all = TRUE)

where by.x is df1 in this case and by.y is df2. It helps you to merge by columns containing the same data but having different names. Good luck!

answered Dec 06 '16 at 09:04

Milosz

1 Answers1