[R] RV: by sentence

[Erin Hodgess]

Hello, Jorge!

This might help:

> fish.df
   Sex Length
1 male     15
2 fema     20
3 fema     17
4 fema     19
5 male     18
> str(fish.df)
'data.frame':   5 obs. of  2 variables:
 $ Sex   : Factor w/ 2 levels "fema","male": 2 1 1 1 2
 $ Length: int  15 20 17 19 18
> tapply(fish.df$Length,fish.df$Sex,mean)
    fema     male 
18.66667 16.50000 
>

Sincerely,
Erin Hodgess
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: hodgess at gator.uhd.edu

From: "Jorge Cornejo Donoso" <jfc10816 at ucsc.edu>
Subject: [R] RV: By sentence




Hi dear listers

	Do you know how to made a mean by one or more categorical variables?
	I can do that quite easy on SAS by in R I just can't do it E.g.
	Some fishes
	Sex 	Lenght
	male	15
	fema	20
	fema	17
	fema	19
	male  18

	So the idea is mean(Lenght) by sex, in order to have sex: Male
mean=XX Sex: Fema mean=YY
	In this case is quite easy to do it by a loop, but I have a huge DB
so is not an option. Any suggestion?

	Thanks in advance!

--

Jorge Cornejo Donoso

Universidad Austral de Chile