I have a dataframe with numeric entries. The entries all consist of numbers that are at least 4 or multiples of four. I would now like to separate the numbers so all of them consit of four digits and are separated by either a ',' or in a seperate column.

y<-c(17938289, 123458938, 780983483029)

x<-c(0,1,2)

df<-data.frame(x,y)

df

x y

1 0 17938289

2 1 12345893

3 2 780983483029

The entry for y1 should be like: 1793, 8289

The entry for the next row should be 1234, 5893 etc.

Unfortunately I have no clue how to fix this problem. I'd be grateful for some help!