[R] bug with subset and plot?

Ista Zahn istazahn at gmail.com
Fri Aug 7 19:29:58 CEST 2009


See http://wiki.r-project.org/rwiki/doku.php?id=tips:data-manip:drop_unused_levels

-Ista
> 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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