http://stackoverflow.com/questions/1195826/dropping-factor-levels-in-a-subsetted-data-frame-in-r-----Original Message-----

From:

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[hidden email]] On Behalf Of Knut Helge Jensen

Sent: Friday, August 07, 2009 5:02 AM

To:

[hidden email]
Subject: [R] bug with subset and plot?

Hi!

I have the following problem that I beleive is a bug:

I have a dataframe with one categorical and one numerical vector. The

categorical vector has three levels (uc, up and vc). A plot of the

vectors with the categorical vector on the x-axis gives a boxplot with

three boxes - exactly as expected.

If I then use the subset function to make a dataset that only includes

two of the levels of the categorical vector and do the plot again, all

three levels are still shown on the x-axis even though one of them

doesn't exist in the dataset. The plot shows correct number of boxes (2).

The whole syntax for what I describe is as follows:

exploration.df <- read.table('clipboard', header=T)

attach(exploration.df)

plot(treatment,total.escapes)

exp.df <- subset(exploration.df, treatment!='up')

attach(exp.df)

plot(treatment, total.escapes)

I use R version 2.9.1 (2009-06-26) for Debian.

Knut Helge Jensen

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