I came across some weird behavior in R. Imagine that I have this data frame, and I want to change the names of the columns by using colnames and a vector:
df <- data.frame(a = seq(1,10), b = seq(11,20), c = seq(31,40))
colnames(df) <- c(`b` = 'B1', `a` = 'A2', `c` = 'C3')
This gives the following df:
B1 A2 C3
1 1 11 31
2 2 12 32
3 3 13 33
4 4 14 34
5 5 15 35
6 6 16 36
7 7 17 37
8 8 18 38
9 9 19 39
10 10 20 40
Notice that the data is still in the same order. So, a is actually replaced with 'B1' and b is replaced with 'A2'. But, it should look like this if colnames paid attention to the name specification:
A2 B1 C3
1 1 11 31
2 2 12 32
3 3 13 33
4 4 14 34
5 5 15 35
6 6 16 36
7 7 17 37
8 8 18 38
9 9 19 39
10 10 20 40
It seems that colnames is completely ignoring the name specification.
I understand the simple solution is to just order the names how you want them saved. However, I want to know if there is a way to specify them in a vector and for that vector to match the old name to the new name. This is just a simple example, what I actually have is more complicated.
What I want to do is ensure that whenever I am renaming column names, they are replaced in the appropriate way so that when I combine dataframes the data under the column name is matched as intended.
You can use match function in base R:
df <- data.frame(a = seq(1,10), b = seq(11,20), c = seq(31,40))
new_names <- c(`b` = 'B1', `a` = 'A2', `c` = 'C3')
colnames(df)[match(names(new_names), colnames(df))] <- new_names