[R] ggplot / reshape: basic usage

From: baptiste Auguié <ba208_at_exeter.ac.uk>
Date: Wed, 23 Jan 2008 15:44:38 +0000


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!



Baptiste Auguié

Physics Department
University of Exeter
Stocker Road,
Exeter, Devon,

Phone: +44 1392 264187


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