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hello! i need help for a specific graphic issue

4 messages · Giacomo Prodi, Hadley Wickham, Bart Joosen +1 more

#
hello, ladyes and gentlemans.

check this:

means<-c(4,6,8)
stand.error<-c(0.1,0.3,0.5)

now i've strongly tryed to scatterplot the
means(y-axis),by showing their sd with the
arrow(..,code=3,angle=90) function.
The problem is that my x-axis has categorical values
(say, factor(x)), and the arrows() can't recognize
them as right coordinates.
?????
thank you all in advance
B.F. insubria university (varese)



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#
On Wed, Mar 12, 2008 at 5:37 AM, Giacomo Prodi <bonoricus at yahoo.it> wrote:
This is a bit easier to do with ggplot2:

df <- data.frame(
  trt = factor(c("a", "b", "c")),
  mean = c(4,6,8),
  se = c(0.1,0.3,0.5)
)

install.packages("ggplot2")
library(ggplot2)

qplot(trt, mean, data=df)
qplot(trt, mean, data=df, min=mean - se, max = mean + se, geom="pointrange")

Hadley
#
quick (and dirty) solution:

y.up<- means+stand.error
y.dwn<- means-stand.error

plot(means,ylim=c(3.5,10))
for (i in 1:length(means)) arrows(i,means[i],i,y.up[i],length=0.1)
for (i in 1:length(means)) arrows(i,means[i],i,y.dwn[i],length=0.1)
Giacomo Prodi wrote:

  
    
#
I don't think that you're actually creating a
scatterplot if the x-axis is a factor.  You're getting
a boxplot.

If you want a scatterplot then something like this
might work.
======================================================

means<-c(4,6,8)
stand.error<-c(0.1,0.3,0.5)

aa <- factor(c("A","B","C","A", "C", "C"))
dd <- 1:length(levels(aa))

plot(dd, means, xaxt="n") 
arrows(dd, means + stand.error, dd, means-stand.error,
          code=3, angle=90)
axis(1, at=dd, labels=levels(aa))

=======================================================
--- Giacomo Prodi <bonoricus at yahoo.it> wrote: