[R] error bars for a barchart

[Beatriz De Francisco]

Walmes, Thank you so much!!!
I am still trying to understand all of your code but it works. I have changed it a bit so that I get upper and lower limits for the error bar, and that the origin starts at 0 so the negative values are plotted correctly.

barchart(Change~fTreat,groups=Process,change,
         stderr=change$stderr,
         ylab="Pocertage change",
         xlab="Treatment",
         #ylim=-115:50,
         scales=list(alternating=FALSE,
                     tick.number=7,
                     tck=c(-1,0)),
         prepanel=function(y, stderr, subscripts=subscripts, ...){
           uy <- as.numeric(y+stderr[subscripts])
           ly <- as.numeric(y-stderr[subscripts])
           list(ylim=range(y,uy,ly, finite=TRUE))
         },
         panel=
           function(x, y, subscripts, groups, stderr, box.ratio, ...){
             panel.barchart(x, y, subscripts=subscripts,
                            groups=groups, box.ratio=box.ratio,origin=0, ...)
             panel.abline(h=0,col="black",...)
             d <- 1/(nlevels(groups)+nlevels(groups)/box.ratio)
             g <- (as.numeric(groups[subscripts])-1); g <- (g-median(g))*d
             panel.arrows(as.numeric(x)+g,y-stderr[subscripts], as.numeric(x)+g, y+stderr[subscripts],
                          code=3,angle=90, length=0.025)
           }
         )
I am very new to creating function and would be great if you could explain what the d and g elemens actually do?
this is just for me to understand and later maybe make my own functions. I am assuming that g centers the error bars? but d?

Regards

Beatriz de Francisco Mora
PhD Student
The Scottish Association for Marine Science
Scottish Marine Institute
Oban
PA37 1QA
Tel: 06131 559000 (switchboard)
Fax: 01631559001
E. beatriz.defrancisco at sams.ac.uk
http://www.smi.ac.uk/beatriz-de-franciso
________________________________________
From: r-help-bounces at r-project.org [r-help-bounces at r-project.org] on behalf of ilai [keren at math.montana.edu]
Sent: 02 May 2012 04:14
To: Walmes Zeviani
Cc: r-help at r-project.org
Subject: Re: [R] error bars for a barchart

Thank you for your example. I only skimmed it, but since both
solutions use nlevels and box.ratio it is no surprise we end up at the
same place (although I do think your g-median is nicer than my 3/4).

Thing is, I wouldn't call either of these "simple"... would be nice if
one could just query the "new" centers, but I don't know if there is a
way without hacking panel.barchart itself ?

Cheers

On Tue, May 1, 2012 at 1:34 PM, Walmes Zeviani <walmeszeviani at gmail.com> wrote:
> I have a repoducibe example here
>
> http://ridiculas.wordpress.com/2011/11/23/media-e-desvio-padrao-de-muitas-variaveis-separado-por-grupos/
>
> Sorry for it be in Portuguese.
>
> Walmes.
>
> ==========================================================================
> Walmes Marques Zeviani
> LEG (Laboratório de Estatística e Geoinformação, 25.450418 S, 49.231759 W)
> Departamento de Estatística - Universidade Federal do Paraná
> fone: (+55) 41 3361 3573
> VoIP: (3361 3600) 1053 1173
> e-mail: walmes at ufpr.br
> twitter: @walmeszeviani
> homepage: http://www.leg.ufpr.br/~walmes
> linux user number: 531218
> ==========================================================================

______________________________________________
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.
The Scottish Association for Marine Science (SAMS) is registered in Scotland as a Company Limited by Guarantee (SC009292) and is a registered charity (9206). SAMS has an actively trading wholly owned subsidiary company: SAMS Research Services Ltd a Limited Company (SC224404). All Companies in the group are registered in Scotland and share a registered office at Scottish Marine Institute, Oban Argyll PA37 1QA. The content of this message may contain personal views which are not the views of SAMS unless specifically stated. Please note that all email traffic is monitored for purposes of security and spam filtering. As such individual emails may be examined in more detail.