[R] removed data is still there!

[Nikhil Kaza]

example(factor)

iris1$Species <- factor(iris1$Species, drop=T)

will get you what you need.


Nikhil Kaza
Asst. Professor,
City and Regional Planning
University of North Carolina

nikhil.list at gmail.com

On Sep 21, 2010, at 7:41 AM, pdb wrote:

>
> I'm confused, hope someone can point out what is not obvious to me.
>
> I thought I was creating a new data frame by 'deleting' rows from an
> existing dataframe - I've tried 2 methods.
>
> But this new data frame seems to remember values from its parent -  
> even
> though there are no occurences.
>
> Where does it get the values versicolor  and virginica from and give  
> then a
> count of 0?
>
> What am I missing?
>
> Thanks in advance.
>
>> summary(iris$Species)
>    setosa versicolor  virginica
>        50         50         50
>
>> nrow(iris)
> [1] 150
>
>> iris1 <- iris[iris$Species == 'setosa',]
>
>> nrow(iris1)
> [1] 50
>
>> summary(iris1$Species)
>    setosa versicolor  virginica
>        50          0          0
>
> boxplot(Petal.Width ~ Species, data = iris1, plot=1)
>
>> iris2 <- subset(iris, Species == 'setosa')
>
>> nrow(iris2)
> [1] 50
>
>> summary(iris2$Species)
>    setosa versicolor  virginica
>        50          0          0
>
>> boxplot(Petal.Width ~ Species, data = iris2, plot=1)
>
>
>
>
> -- 
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