R help - Sep 2012 - Drawing asymmetric error bars

Hello,

I have data which I have arcsin transformed to analyse.
I want to plot my data with error bars however as my data is
back-transformed my standard errors are uneven.
Is there a simple way to draw these asymmetric error bars in R?

Thanks for your help.

	[[alternative HTML version deleted]]

On Sep 27, 2012, at 5:59 AM, Alexandra Howe <ah677 at st-andrews.ac.uk>
wrote:
> Hello,
> 
> I have data which I have arcsin transformed to analyse.
> I want to plot my data with error bars however as my data is
> back-transformed my standard errors are uneven.
> Is there a simple way to draw these asymmetric error bars in R?
> 
> Thanks for your help.


See ?segments or perhaps easier, ?arrows with an 'angle = 90' argument.

Regards,

Marc Schwartz

You can always roll your own with something like:
> x1 <- c(4, 5, 7)
> x2 <- c(5, 6, 9)
> plot(c(1.5, 2.5), cbind(x1[2], x2[2]), xlab="",
ylab="",
     xlim=c(1, 3), ylim=c(0, 10), xaxt="n")
> axis(1, at=1:2+.5, labels=c("Group 1", "Group 2"))
> arrows(1.5, x1[2], 1.5, c(x1[1], x1[3]), angle=90, length=1/8)
> arrows(2.5, x2[2], 2.5, c(x2[1], x2[3]), angle=90, length=1/8)
----------------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77843-4352
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Alexandra Howe
> Sent: Thursday, September 27, 2012 5:59 AM
> To: r-help at r-project.org
> Subject: [R] Drawing asymmetric error bars
> 
> Hello,
> 
> I have data which I have arcsin transformed to analyse.
> I want to plot my data with error bars however as my data is
> back-transformed my standard errors are uneven.
> Is there a simple way to draw these asymmetric error bars in R?
> 
> Thanks for your help.
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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.

On 09/27/2012 08:59 PM, Alexandra Howe wrote:
> Hello,
>
> I have data which I have arcsin transformed to analyse.
> I want to plot my data with error bars however as my data is
> back-transformed my standard errors are uneven.
> Is there a simple way to draw these asymmetric error bars in R?
>
Hi Alexandra,
Have a look at the "dispersion" function in the plotrix package.

Jim