Hi,

I have a two columns data, the first column are values, and second column
are the groups. For this example, there are 3 groups 1,2,3.

How can I manipulate the values in the first column according to groups, say
I would like to find mean, sum, and standard deviation for the different
groups ? How do I plot data according to groups ?

> t <- matrix(c(rnorm(10), 1,1,2,2,1,3,3,3,3,2), ncol=2)

	[[alternative HTML version deleted]]

