[R] Error bar

[Jim Lemon]

On 04/07/2010 03:49 AM, ogbos okike wrote:
> Hi there,
> Using the code below I generated the plot attached. The error bars at day =
> -3, 2 and 4 appear are larger. I was thinking if there is a way I could make
> all the error bars to be of the same size. I don't know if that makes sense.
> If not, then, is there a way I can plot only these 3 largest errorbars at
> day axis (day = -3, 2 and 4) and omit the rest of the error bars.
> I would be much obliged for any help

Hi Ogbos,
It doesn't make much sense to force the error bars to the same size, for 
if you do, they don't tell you anything useful. Obviously days -3, 2 and 
4 had more widely varying temperatures than the others on the plot. You 
could plot the daily means with:

plot(day,means,ylim=c(0,20),type="b",...)

and then set all of the small standard errors to NA:

ciw[ciw<5]<-NA

and use one of the error bar functions:

library(plotrix)
dispersion(day,means,ciw)

I use dispersion because I know that it ignores NA values. Other error 
bar functions probably do this as well.

Jim