How to create new column based on two different length dataframe matching IDS in R

Question

I have df1 with length 100 looks like

PID
123
234
T345
P456
567

and I have another df2 with length 1000 looks like same

PID
123
234
567
T678
P768
....

I need to create new column in df1 if it matches PID with df2 status as "1" or "0"

Expected output :

PID    V1
123     1
234     1
T345    0
P456    0
567     1

I tried ifelse condition but error occured due to uneven length .

Thanks in advance

Answer 1

I would suggest a base R approach with match() and the use ifelse:

#Data
df1 <- structure(list(PID = c("123", "234", "T345", "P456", "567")), class = "data.frame", row.names = 2:6)
df2 <- structure(list(PID = c("123", "234", "567", "T678", "P768")), row.names = 2:6, class = "data.frame")

Now the code using a matching between values and then formating to 0 or 1:

#Match
df1$NewVar <- df2[match(df1$PID,df2$PID),'PID']
df1$NewVar <- ifelse(is.na(df1$NewVar),0,1)

The output:

   PID NewVar
1  123      1
2  234      1
3 T345      0
4 P456      0
5  567      1

Answer 2

You can try %in% like below

df1$V1 <- +(df1$PID %in% df2$PID)

which gives

> df1
   PID V1
1  123  1
2  234  1
3 T345  0
4 P456  0
5  567  1

Data

> dput(df1)
structure(list(PID = c("123", "234", "T345", "P456", "567"), 
    V1 = c(1L, 1L, 0L, 0L, 1L)), row.names = c(NA, 5L), class = "data.frame")
> dput(df2)
structure(list(PID = c("123", "234", "567", "T678", "P768")), row.names = c(NA, 
5L), class = "data.frame")