Merging all the colunms in R with colunm names

Question

I have the following data

> df
X1  X2  X3 
1   3   4  
1   0   0  
1   1   0 

and I want to merge all the column so that the final output will

Answer 1

You can try stack

> setNames(stack(df),c("new","colName"))
  new colName
1   1      X1
2   1      X1
3   1      X1
4   3      X2
5   0      X2
6   1      X2
7   4      X3
8   0      X3
9   0      X3

Data

> dput(df)
structure(list(X1 = c(1L, 1L, 1L), X2 = c(3L, 0L, 1L), X3 = c(4L, 
0L, 0L)), class = "data.frame", row.names = c(NA, -3L))