[R] summary with variance / sd

[Jörg Groß]

Hi,

I have a data frame and would like to have summary statistics for  
grouped data.

With summary() I get the central tendencies for the overall data.


How can I get descriptive statistics with variances and standard  
deviations?


for example my data.frame:

group	x	y
exp		2	4
exp		3	5
exp		2	4
control	1	2
control	2	3
control	1	2


now I want tables with summary statistics (variances included) for  
each group.

Is there an easy way to get this?