In R, how to split/subset a data frame by factors in one column?

按照某列的值拆分data.frame

My data is like this (for example):

ID  Rate    State
1   24  AL
2   35  MN
3   46  FL
4   34  AL
5   78  MN
6   99  FL

I want to split the data by state and I want to get 3 data sets like below:

data set 1
ID  Rate    State
1   24  AL
4   34  AL
data set 2
ID  Rate    State
2   35  MN
5   78  MN
data set 3
ID  Rate    State
3   46  FL
6   99  FL
split( df , df$State )
$AL
  ID Rate State
1  1   24    AL
4  4   34    AL

$FL
  ID Rate State
3  3   46    FL
6  6   99    FL

$MN
  ID Rate State
2  2   35    MN
5  5   78    MN
mylist <- split( df , df$State ) ; 
mylist[[1]]