[R] Beginner question: select cases
ONKELINX, Thierry
Thierry.ONKELINX at inbo.be
Mon Sep 25 14:11:44 CEST 2006
Your problem would be a lot easier if you coded the location in one
variable instead of three variables. Then you could calculate the means
with one line of code:
by(results$q1, results$location, mean)
With your dataset you could use
by(results$London, results$location, mean)
by(results$Rome, results$location, mean)
by(results$Vienna, results$location, mean)
see ?by for more information
And take a good look at your code. You take a subset from results and
the assign it to results. This means that you replace the original
results dataframe with a subset of it. As you take the subset for the
next city, you won't take a subset from the original dataset but for the
previous subset!
Cheers,
Thierry
------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Reseach Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
Thierry.Onkelinx op inbo.be
www.inbo.be
-----Oorspronkelijk bericht-----
Van: r-help-bounces op stat.math.ethz.ch
[mailto:r-help-bounces op stat.math.ethz.ch] Namens Peter Wolkerstorfer -
CURE
Verzonden: maandag 25 september 2006 13:51
Aan: r-help op stat.math.ethz.ch
Onderwerp: [R] Beginner question: select cases
Hello all,
I hope i chose the right list as my question is a beginner-question.
I have a data set with 3 colums "London", "Rome" and "Vienna" - the
location is presented through a 1 like this:
London Rome Vienna q1
0 0 1 4
0 1 0 2
1 0 0 3
....
....
....
I just want to calculate the means of a variable q1.
I tried following script:
# calculate the mean of all locations
results <- subset(results, subset== 1 )
mean(results$q1)
# calculate the mean of London
results <- subset(results, subset== 1 , select=c(London))
mean(results$q1)
# calculate the mean of Rome
results <- subset(results, subset== 1 , select=c(Rome))
mean(results$q1)
# calcualate the mean of Vienna
results <- subset(results, subset== 1 , select=c(Vienna))
mean(results$q1)
As all results are 1.68 and there is defenitely a difference in the
three locations I wonder whats going on.
I get confused as the Rcmdr asks me to overwrite things and there is no
"just filter" option.
Any help would be apprechiated. Thank you in advance.
Regards
Peter
___CURE - Center for Usability Research & Engineering___
Peter Wolkerstorfer
Usability Engineer
Hauffgasse 3-5, 1110 Wien, Austria
[Tel] +43.1.743 54 51.46
[Fax] +43.1.743 54 51.30
[Mail] wolkerstorfer op cure.at
[Web] http://www.cure.at
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