[R] ggplot / reshape: basic usage

[baptiste Auguié]

Hi,

I've been trying to do the following simple thing: given a data.frame,

> library(reshape)
> library(ggplot2)
>
> df <- data.frame(x=c(1:10),y=sin(1:10),z=cos(1:10))
> dfm<-melt(df, id=c("x"), measured=c("y","z"))


i want to plot  y and z against x, and add vertical errorbars to the  
points corresponding to the standard deviation of y and z respectively.

I tried the following, inspired by some previous post in the list,

> se <- function(x) sd(x)/sqrt(length(x))
> means <- cast(dfm, variable~., function(x) c(se = se(x)))
>
> qplot(value,x, data=means, colour=variable, min = value - se, max =
>  value + se, geom=c("point","errorbar"))


but this fails, as I obviously don't get the philosophy behind the  
"cast" function.

Any advice welcome!

Thanks,

baptiste

_____________________________

Baptiste Auguié

Physics Department
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag
http://projects.ex.ac.uk/atto