R help - Jan 2011 - adding error bars

Dear all,
I am trying to add error bars on a boxplot but have encountered an error as
indicated below. Is there a package I need to install or a library I have to
load before this goes please.
Thanks for any idea.
Ogbos

x<-replicate(20,rnorm(50))
 boxplot(x,notch=TRUE,main="Notched boxplot with error bars")
 error.bars(x,add=TRUE)
Error: could not find function "error.bars"

	[[alternative HTML version deleted]]

Hi,

You will find package "sos" has some handy functions for searching for
functions/packages:

###########################
install.packages("sos")
require(sos)
findFn("error.bars")
###########################

Perhaps the "psych" package has the error.bars() function you are
thinking of?

As a side note, I am not sure it makes much sense to add error bars to
a boxplot---it already includes 25th/75th percentiles (at least
approximately, some use hinges, etc. but same general idea), and
typically minimum and maximum scores.  What would the error bars add
to that picture that would aid a viewer in understanding the
distribution of your data or the difference between different sets of
data?  In other words, is the information conveyed over and above the
boxplots large enough to warrant the additional clutter, possible
confusion, and necessary key/description in your figure caption so
viewers know what they are looking at?  Just something to think about.

Cheers,

Josh

On Wed, Jan 26, 2011 at 10:04 AM, ogbos okike <ogbos.okike at gmail.com>
wrote:
>
> Dear all,
> I am trying to add error bars on a boxplot but have encountered an error as
> indicated below. Is there a package I need to install or a library I have
to
> load before this goes please.
> Thanks for any idea.
> Ogbos
>
> x<-replicate(20,rnorm(50))
> ?boxplot(x,notch=TRUE,main="Notched boxplot with error bars")
> ?error.bars(x,add=TRUE)
> Error: could not find function "error.bars"
>
> ? ? ? ?[[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.


--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/

On 01/27/2011 05:04 AM, ogbos okike wrote:
> Dear all,
> I am trying to add error bars on a boxplot but have encountered an error as
> indicated below. Is there a package I need to install or a library I have
to
> load before this goes please.
> Thanks for any idea.
> Ogbos
>
> x<-replicate(20,rnorm(50))
>   boxplot(x,notch=TRUE,main="Notched boxplot with error bars")
>   error.bars(x,add=TRUE)
> Error: could not find function "error.bars"
Hi Ogbos,
Adding "error bars" is easy, but as Josh pointed out, may not mean
much.
If you are seeking to illustrate a confidence interval for the median, 
it may be better to use points or symbols and error bars rather than 
boxplots.

Jim

Have you tried using the arrows function with angle = 90? you will have to
create a mean and standard error variable

-----
- AK
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