R help - Dec 2009 - lattice: adding information on number of observations

Dear R-users,

I am using R version 2.9.1 and lattice 0.17-26 under windows.
In a lattice boxplot, I would like to add information on how many observations
each singel boxplot is based upon.

For example (the basic plot):
# Begin R-code
library(lattice)
dat <- data.frame(panvar =
rep(c("A","B","A","B"), c(3,7,4,6)), grp
= rep(c("grp1", "grp2"), c(10,10)), val = rnorm(20))
dat
bwplot(val ~ grp | panvar, data = dat)
# End R-code

As in my real life data the number of observations in each subgroup will be
quite different, I would like to include the number of observations each boxplot
is based upon.
Aggregation will tell me the numbers:
# Begin R-code
aggregate(dat$val, by = list(dat$panvar, dat$grp), FUN = length)
# End R-code
But how to match these numbers with the plot (so that for example
"n=3" will be written as text beneath panel A/group1)?

Any advice would be appreciated;
kind regards
Heinrich.

Depends on exactly how / where you want to display the text.

One approach (showing text inside each panel, at the bottom):

bwplot(val ~ grp | panvar, data = dat,
  panel = function(x, y, ...) {
    panel.bwplot(x, y, ...)
    nn <- table(x)
    panel.text(paste("n =", nn), x = seq_along(nn),
               y = current.panel.limits()$y[1], pos = 3)
  })


2009/12/2 RINNER Heinrich <HEINRICH.RINNER at
tirol.gv.at>:
> Dear R-users,
>
> I am using R version 2.9.1 and lattice 0.17-26 under windows.
> In a lattice boxplot, I would like to add information on how many
observations each singel boxplot is based upon.
>
> For example (the basic plot):
> # Begin R-code
> library(lattice)
> dat <- data.frame(panvar =
rep(c("A","B","A","B"), c(3,7,4,6)), grp
= rep(c("grp1", "grp2"), c(10,10)), val = rnorm(20))
> dat
> bwplot(val ~ grp | panvar, data = dat)
> # End R-code
>
> As in my real life data the number of observations in each subgroup will be
quite different, I would like to include the number of observations each boxplot
is based upon.
> Aggregation will tell me the numbers:
> # Begin R-code
> aggregate(dat$val, by = list(dat$panvar, dat$grp), FUN = length)
> # End R-code
> But how to match these numbers with the plot (so that for example
"n=3" will be written as text beneath panel A/group1)?
>
> Any advice would be appreciated;
> kind regards
> Heinrich.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Felix Andrews / ???
Postdoctoral Fellow
Integrated Catchment Assessment and Management (iCAM) Centre
Fenner School of Environment and Society [Bldg 48a]
The Australian National University
Canberra ACT 0200 Australia
M: +61 410 400 963
T: + 61 2 6125 4670
E: felix.andrews at anu.edu.au
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The boxplot with sample size information is one of the features
included in the HH package.
An example is posted on my site
http://astro.ocis.temple.edu/~rmh/HH/bwplot-color.pdf

In this example I show grouping, control of x-axis position, multiple
x-axis labels, and
control of display of extreme outliers.

Rich