[R] aggregate and the $ operator

[Ed Siefker]

So that's how that works!  Thanks.

On Fri, Jan 22, 2016 at 1:32 PM, Joe Ceradini <joeceradini at gmail.com> wrote:
> Does this do what you want?
>
> aggregate(Nuclei ~ Slide, example, sum)
>
> On Fri, Jan 22, 2016 at 12:20 PM, Ed Siefker <ebs15242 at gmail.com> wrote:
>>
>> Aggregate does the right thing with column names when passing it
>> numerical coordinates.
>> Given a dataframe like this:
>>
>>   Nuclei Positive Nuclei Slide
>> 1    133              96    A1
>> 2     96              70    A1
>> 3     62              52    A2
>> 4     60              50    A2
>>
>> I can call 'aggregate' like this:
>>
>> > aggregate(example[1], by=example[3], sum)
>>   Slide Nuclei
>> 1    A1    229
>> 2    A2    122
>>
>> But that means I have to keep track of which column is which number.
>> If I try it the
>> easy way, it doesn't keep track of column names and it forces me to
>> coerce the 'by'
>> to a list.
>>
>> > aggregate(example$Nuclei, by=list(example$Slide), sum)
>>   Group.1   x
>> 1      A1 229
>> 2      A2 122
>>
>> Is there a better way to do this?  Thanks
>> -Ed
>>
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>
>
>
>
> --
> Cooperative Fish and Wildlife Research Unit
> Zoology and Physiology Dept.
> University of Wyoming
> JoeCeradini at gmail.com / 914.707.8506
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>