[R] Query about getting averages across a certain parameter in a table

[lalitha viswanath]

Hi
I have a table that goes 
data

cluster_ac  clockrate age class
7337         0.9       0.001  alpha_proteins
7888         0.1       0.78   beta proteins

etc

The class column can have 7-8 different unique values
While the clockrate and age columns are floats varying
from 0 to 1.

I wish to get the average clockrate across each of the
classes for this data.

I would appreciate your help regarding the aboe.

Thanks
Lalitha