How to append group row into dataframe

Question

I have this df1:

A B C
1 2 3
5 7 9

where A B C are columns names.

I have another df2 with one column:

A
1
         


        

Answer 1

Data:

df1 <- data.frame(A=c(1,5),
                  B=c(2,7),
                  C=c(3,9))
df2 <- data.frame(A=c(1,2,3,4))

Solution:

df2 <- matrix(rep(df2$A, ncol(df1)), ncol=ncol(df1))
colnames(df2) <- colnames(df1)
rbind(df1,df2)

Result:

  A B C
1 1 2 3
2 5 7 9
3 1 1 1
4 2 2 2
5 3 3 3
6 4 4 4