How to make summary table by group in r?

Question

I want make a summary table by group in R
compare several parameter by factor
For example

data(iris)
str(iris)

i wanna make table

     Group   Sepal.Length Sepal.Width Petal.Length Petal.Width
  Species1        mean       mean        mean       mean
  Species2        mean       mean        mean       mean
  Species3        mean       mean        mean       mean 

possible import t.test result
How do i do?

Answer 1

data(iris) 
aggregate(iris[,1:4], list(iris$Species), mean)