Re: [R] Question: how to build a subset to do separate calculations

From: stephen sefick <ssefick_at_gmail.com>
Date: Thu, 24 Jul 2008 16:45:00 -0400

or sapply as I have recently found to be useful.

On Thu, Jul 24, 2008 at 4:33 PM, Erik Iverson <iverson_at_biostat.wisc.edu> wrote:

> Spencer -
>
> Spencer wrote:
>
>>

>> Dear R Experts,
>>
>> I am trying to create several subsets that I want to use as separate
>> datasets. After separate subsets are created for each country, I want to do
>> some calculations for each. I did the following:
>>
>> data <- data.frame(na.omit(read.spss("trial.sav")))
>>
>> attach (data)
>>
>
> You might not want to call it 'data' since 'data' is the name of a function
> in base R.
>
> Also, the usual advice is to avoid attaching data.frames to the search
> path, for the exact reasons that happen to you below.
>
>
>> Netherlands <- subset(data, COUNTRY = "NETHERLANDS")
>> attach(Netherlands)
>>
>> But after this step, when I check the summary statistics for
>> "Netherlands," what returns is the summary for the original dataset.
>>
>
> Try typing search() after attaching this to see why. You may have also
> seen a message about objects being masked when you used the second 'attach'
> command; at least I do in my version of R.
>
>
>
>
> I've also tried defining Netherlands as Netherlands <-
>> data.frame(subset(data, COUNTRY = "NETHERLANDS")), but get the same result.
>>
>> Any help would be greatly appreciated!
>>
>
> Don't use attach. If you want to do summaries by country, there are many
> simpler ways. See ?tapply, ?aggregate, and ?by for instance.
>
> Best,
> Erik
>
>
>>
>> Spencer
>>
>>
>> ------------------------------------------------------------------------
>>
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>>
>
> ______________________________________________
> R-help_at_r-project.org mailing list
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> PLEASE do read the posting guide
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>

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Received on Thu 24 Jul 2008 - 20:48:47 GMT

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