R help - Feb 2009 - Grouping stripchart markers

If I have a dataset grouped into 3 classes, how can I construct a 
stripchart where the markers are different for each class, e.g. a cross 
for 1, square for 2 and circle for 3. In the example below I try to 
define the marker type by the class but this only changes all the 
markers from the default squares into circles. I am assuming I need to 
set pch as an argument in par but am unsure how to proceed.

data <- rnorm(9)
class <- c(1,1,1,2,2,2,3,3,3)
x <- data.frame(data,class)
stripchart(x[,1], pch=x[,2])

Thanks,

Sam.

well, for a simple stripchart (i.e., default method) you can use 
something like the following:

x <- rnorm(9)
cl <- c(1,1,1,2,2,2,3,3,3)

plot(range(x), c(0, 1), type = "n", yaxt = "n", ann = FALSE)
points(x, rep(0.5, length(x)), pch = cl)


I hope it helps.

Best,
Dimitris


Sam Player wrote:
> If I have a dataset grouped into 3 classes, how can I construct a 
> stripchart where the markers are different for each class, e.g. a cross 
> for 1, square for 2 and circle for 3. In the example below I try to 
> define the marker type by the class but this only changes all the 
> markers from the default squares into circles. I am assuming I need to 
> set pch as an argument in par but am unsure how to proceed.
> 
> data <- rnorm(9)
> class <- c(1,1,1,2,2,2,3,3,3)
> x <- data.frame(data,class)
> stripchart(x[,1], pch=x[,2])
> 
> Thanks,
> 
> Sam.
> 
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus Medical Center

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