Duplicate Columns when using the merge statement - r

Question

When I try to merge some codes to the code descriptions I get 2 duplicate columns. I start out with this:
Table Name: Test
ID State
1 5
2 2
3 5
and want to merge it with this:
Table Name: statecode
StateID State
5 Mass
2 NY
to make a table like this:
ID State
1 Mass
2 NY
3 Mass
However, I get a table like this:
ID State State
1 5 Mass
2 2 NY
3 5 Mass
I used the merge command like this:
test = merge(x = test, y = statecode, by.x = "State", by.y = "StateID", all.x = T)
Is there a better function other than merge to use in this case? Maybe one to just replace the state code with the state name?
Thank you very much for the help!

Answer 1

You do have to say which column you want to drop, but you can express it concisely using dplyr, for example.
Generating sample data based on yours (but correcting the column names):
test <- read.table(text =
"ID StateID
1 5
2 2
3 5", header = TRUE)
statecode <- read.table(text =
"
StateID State
5 Mass
2 NY", header = TRUE)
Using dplyr:
library(dplyr)
test %>% left_join(statecode, by = "StateID") %>% select(-StateID)
ID State
1 1 Mass
2 2 NY
3 3 Mass

Answer 2

Another way with base R:
Pmerge <- function(df1, df2) {
res <- suppressWarnings(merge(df1, df2, by.x = "State", by.y = "Code", all.x = T)[,-1])
newdf <- res[order(res$ID),]
row.names(newdf) <- 1:nrow(newdf)
newdf
}
Pmerge(Test, statecode)
ID State
1 1 Mass
2 2 NY
3 3 Mass