Binding columns with similar column names in the same dataframe in R

Question

I have a data frame that looks somewhat like this:

df <- data.frame(0:2, 1:3, 2:4, 5:7, 6:8, 2:4, 0:2, 1:3, 2:4)
colnames(df) <- rep(c(\'a\', \'b\', \         


        

Answer 1

This will do the trick, I suppose.

Explanation

df[,names(df) == 'a'] will select all columns with name a

unlist will convert above columns into 1 single vector

unname will remove some stray rownames given to these vectors.

unique(names(df)) will give you unique column names in df

sapply will apply the inline function to all values of unique(names(df))

> df
  a b c a b c a b c
1 0 1 2 5 6 2 0 1 2
2 1 2 3 6 7 3 1 2 3
3 2 3 4 7 8 4 2 3 4
> sapply(unique(names(df)), function(x) unname(unlist(df[,names(df)==x])))
      a b c
 [1,] 0 1 2
 [2,] 1 2 3
 [3,] 2 3 4
 [4,] 5 6 2
 [5,] 6 7 3
 [6,] 7 8 4
 [7,] 0 1 2
 [8,] 1 2 3
 [9,] 2 3 4