[R] removed data is still there!

[Prof Brian Ripley]

On Fri, 24 Sep 2010, Prof Brian Ripley wrote:

> 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]

I don't know what happened there:

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

is what I saw before sending.

>
> 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)
>>>> 
>>>> 
>>>> 
>>>> 
>>>> --
>>>> View this message in context: 
>>>> http://r.789695.n4.nabble.com/removed-data-is-still-there-tp2548440p2548440.html
>>>> Sent from the R help mailing list archive at Nabble.com.
>>>> 
>>>> ______________________________________________
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>>>> PLEASE do read the posting guide 
>>>> http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>> 
>> 
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide 
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>> 
>
> -- 
> 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
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
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