R help..subsetting data frame that meeting multiple criteria

Hi,
I am new to R.  I am trying to regroup data frame using multiple constrains.
for example

data frame: data
   value	class	percent
15526	36	4.6875
15527	62	85.9375
15527	82	32.4564
15528	36	70.3125
15528	62	9.375
15528	82	74.6875

I need to regroup each class that have greater than or equal to 70 percent
into new group. Similarly, I also need to regroup each class that have less
than 70 percent into new group.

I can do this by using following syntax for each class
class36<- data[data$class==36&data$percent>70,]
class36a<- data[data$class==36&data$percent<=70,]
but I have 100 different classes. In order to do this for all 100 classes, I
have write that syntax 100 times. There would be some way to do dynamically
to regroup for 100 classes (may be using for loop) but I dont know. Can you
please help in this.
Output should be like
data frame: class36
value	class	percent
15528	36	70.3125

data frame: class36a
value	class	percent
15526	36	4.6875

data frame: class62
15527	62	85.9375

data frame: class62a
15528	62	9.375

data frame: class82
15528	82	74.6875

data frame: class82a
15527	82	32.4564

Thank you very much your help..
P.



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