[R] Newbie question on subsets

[Bill.Venables at csiro.au]

This is very standard problem for neophytes.  Subsetting a factor does
not automatically subset the levels, so the all appear in the boxplot.


I think the simplest way round this is to replace ~ country in the
formula by ~ factor(country).  The call to factor() will re-set the
levels to only those which appear.  So try

boxplot(log(marketvalue) ~ factor(country),  ## changed line
   data = subset(Forbes2000,
                 country %in%
	c("United Kingdom","Germany","India","Turkey")),
   ylab = "log(marketvalue)", varwidth = TRUE)

Bill Venables. 

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Joe Trubisz
Sent: Sunday, 20 January 2008 1:12 PM
To: R-help at r-project.org
Subject: [R] Newbie question on subsets

Hi...

I'm working through the book, A Handbook of Statistical Analyses  
using R by Everitt, and I'm trying to do the following (p. 19 of his  
book):

boxplot(log(marketvalue) ~ country,
   data = subset(Forbes2000,
                 country %in% 
	c("United Kingdom","Germany","India","Turkey")),
   ylab = "log(marketvalue)", varwidth = TRUE)

This *almost* works, but I'm getting ALL the countries on the x-axis,  
not just the 4-specified.
I tried tinkering with variations in the subset command to no avail.

Can someone tell me what's wrong/missing with the above command?

Thanks,
Joe

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