[R] removed data is still there!

[Prof Brian Ripley]

On Thu, 23 Sep 2010, Peter Ehlers wrote:

> On 2010-09-21 5:51, Nikhil Kaza wrote:
>> example(factor)
>> 
>> iris1$Species<- factor(iris1$Species, drop=T)
>> 
>> will get you what you need.
>
> Hmm, doesn't work for me. ?factor does not list a 'drop='
> argument.

I suspect

iris1$Species <- [iris1$Species, drop=TRUE]

was meant.  See ?`[.factor` .

>
>  -Peter Ehlers
>
>> 
>> 
>> 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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>>> 
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>> 
>
> ______________________________________________
> R-help at r-project.org mailing list
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>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595