[R] question about "mean"

From: SH.Chou <cls3415_at_gmail.com>
Date: Wed, 09 Jun 2010 17:43:29 -0500


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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Received on Thu 10 Jun 2010 - 02:18:59 GMT

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