How to split a data frame?

Question

I want to split a data frame into several smaller ones. This looks like a very trivial question, however I cannot find a solution from web search.

Answer 1

You may also want to cut the data frame into an arbitrary number of smaller dataframes. Here, we cut into two dataframes.

x = data.frame(num = 1:26, let = letters, LET = LETTERS) set.seed(10) split(x, sample(rep(1:2, 13))) 

gives

$`1`    num let LET 3    3   c   C 6    6   f   F 10  10   j   J 12  12   l   L 14  14   n   N 15  15   o   O 17  17   q   Q 18  18   r   R 20  20   t   T 21  21   u   U 22  22   v   V 23  23   w   W 26  26   z   Z  $`2`    num let LET 1    1   a   A 2    2   b   B 4    4   d   D 5    5   e   E 7    7   g   G 8    8   h   H 9    9   i   I 11  11   k   K 13  13   m   M 16  16   p   P 19  19   s   S 24  24   x   X 25  25   y   Y 

You can also split a data frame based upon an existing column. For example, to create three data frames based on the cyl column in mtcars:

split(mtcars,mtcars$cyl) 

Answer 2

If you want to split a dataframe according to values of some variable, I'd suggest using daply() from the plyr package.

library(plyr) x <- daply(df, .(splitting_variable), function(x)return(x)) 

Now, x is an array of dataframes. To access one of the dataframes, you can index it with the name of the level of the splitting variable.

x$Level1 #or x[["Level1"]] 

I'd be sure that there aren't other more clever ways to deal with your data before splitting it up into many dataframes though.