One possibility is
aggregate(iris[,-5],list(iris[,5]),mean)
Group.1 Sepal.Length Sepal.Width Petal.Length Petal.Width
1 setosa 5.006 3.428 1.462 0.246
2 versicolor 5.936 2.770 4.260 1.326
3 virginica 6.588 2.974 5.552 2.026
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
[email protected]
On Wed, 9 Jun 2010, SH.Chou wrote:
Hi there:
I have a question about generating mean value of a data.frame. Take
iris data for example, if I have a data.frame looking like the following:
---------------------
Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1 5.1 3.5 1.4
0.2 setosa
2 4.9 3.0 1.4
0.2 setosa
3 4.7 3.2 1.3
0.2 setosa
. . . .
. .
. . . .
. .
. . . .
. .
-----------------------
There are three different species in this table. I want to make a table and
calculate mean value for each specie as the following table:
-----------------
Sepal.Length Sepal.Width Petal.Length
Petal.Width
mean.setosa 5.006 3.428 1.462
0.246
mean.versicolor 5.936 2.770 4.260
1.326
mean.virginica 6.588 2.974 5.552
2.026
-----------------
Is there any short syntax can do it?? I mean shorter than the code I wrote
as following:
attach(iris)
mean.setosa<-mean(iris[Species=="setosa", 1:4])
mean.versicolor<-mean(iris[Species=="versicolor", 1:4])
mean.virginica<-mean(iris[Species=="virginica", 1:4])
data.mean<-rbind(mean.setosa, mean.versicolor, mean.virginica)
detach(iris)
------------------
Thanks a million!!!
--
=====================================
Shih-Hsiung, Chou
System Administrator / PH.D Student at
Department of Industrial Manufacturing
and Systems Engineering
Kansas State University
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
