From: Charilaos Skiadas <cskiadas_at_gmail.com>

Date: Fri, 28 Mar 2008 07:49:00 -0400

R-help_at_r-project.org mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Fri 28 Mar 2008 - 11:55:22 GMT

Date: Fri, 28 Mar 2008 07:49:00 -0400

On Mar 28, 2008, at 2:42 AM, Agustin Lobo wrote:

> Thanks for your detailed explanation.

*> You are right, a set of boxplots done with bwplot
**> is a much better graphic for this type of data:
**>
**> bwplot(V1~VAR|f,data=datos2)
**>
**> This was not a good example. The barplot would be suited
**> for counts, ie. species composition:
**> datos4 <- data.frame(V1=round(runif(200,1,5)),SITE=factor(round
**> (runif(200,1,3))))
**>
**> where I would like a barplot of table(V1) for each site:
**> par(mfrow=c(3,1))
**> barplot(table(datos4$V1[datos4$SITE==1]))
**> barplot(table(datos4$V1[datos4$SITE==2]))
**> barplot(table(datos4$V1[datos4$SITE==3]))
**>
**> I'll try with barchart!
*

Perhaps this:

datos5 <- with(datos4,aggregate(rep(1,nrow(datos4)), list
(V1=V1,SITE=SITE),sum))

barchart(x~ordered(V1)|SITE, data=datos5)

> Is there an R guide to Trellis graphics?

I found Paul Murrell's book useful.

*> Agus
*

Haris Skiadas

Department of Mathematics and Computer Science
Hanover College

> Charilaos Skiadas escribió:

*>> On Mar 27, 2008, at 1:47 PM, Agustin Lobo wrote:
**>>> Thanks, it was a matter of reshaping the data matrix as I usually
**>>> have
**>>> it, ie:
**>>> datos <-
**>>> data.frame(x=abs(round(rnorm(100,10,5))),y=abs(round(rnorm
**>>> (100,2,1))),f=factor(round(runif(100,1,3))))
**>>>
**>>> to become:
**>>>
**>>> datos2 <-
**>>> data.frame(V1=c(datos[,1],datos[,2]),"VAR"=c(rep("x",100),rep("y",
**>>> 100)),f=factor(c(datos[,3],datos[,3])))
**>>>
**>>> and then
**>>> require(lattice)
**>>> barchart(V1~VAR|f,data=datos2)
**>>>
**>>> I get horizontal lines in the bars that I do not understand, though.
**>> In order to understand the lines , you should ask: What does the
**>> height of each bar correspond to? As you have set things up, the
**>> "x" bar in panel "1" should somehow correspond to the all values:
**>> datos2$V1[datos2$VAR=="x" & datos2$f==1]
**>> [1] 15 13 14 1 18 14 8 12 7 19 10 1 5 14 7 9 14 7 5 10 6
**>> 12 10 11 11 7 15
**>> [28] 9 4 12 17 10 4 5
**>> So you should ask yourself, how you expect R to produce a single
**>> column, which in some sense corresponds to just one single number,
**>> its height, from these different values. My guess is that you want
**>> R to show you just the mean on each group. For me this is not a
**>> barplot, but anyway. What happens in the barplot you have now, I
**>> think, is this that R will start by constructing a bar with height
**>> 15, then put on it a bar of height 13, then on it a bar of height
**>> 14 and so on. So the lines you see account for the boxes that
**>> survive:
**>> > x<-datos2$V1[datos2$VAR=="x" & datos2$f==1]
**>> > unique(cummax(rev(x)))
**>> [1] 5 10 17 19
**>> I would recommend using boxplots instead of "barplots only showing
**>> the means". If you really want barplots of the means, I think you
**>> can do the following:
**>> datos3 <- with(datos2, aggregate(x=V1, by=list(VAR=VAR,f=f), mean))
**>> barchart(x~VAR|f, datos3)
**>> Another option would be ggplot2 I think, but I'll let someone
**>> knowledgeable with that package speak up.
**>>> Agus
**>>>
**>> Haris Skiadas
**>> Department of Mathematics and Computer Science
**>> Hanover College
**>
**> --
**> Dr. Agustin Lobo
**> Institut de Ciencies de la Terra "Jaume Almera" (CSIC)
**> LLuis Sole Sabaris s/n
**> 08028 Barcelona
**> Spain
**> Tel. 34 934095410
**> Fax. 34 934110012
**> email: Agustin.Lobo_at_ija.csic.es
**> http://www.ija.csic.es/gt/obster
*

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