[R] Sum by column
Peter Francis
peterfrancis at me.com
Wed Jan 12 15:39:22 CET 2011
David and Josh,
Thanks very much for your help, it is much appreciated.
Peter
On 12 Jan 2011, at 14:28, David Winsemius wrote:
There are two functions you need to become familiar with:
?tapply
?ave
If you wanted these summed values to be placed in another column of the same dataframe, you would use ave. If you wanted a new structure (somewhat shorter) you would use tapply with sum as the function. E. g:
tapply(ecoregion$ED, ecoregion$ECOCODE, sum)
--
David.
On Jan 12, 2011, at 5:38 AM, Peter Francis wrote:
> Dear List,
>
> I have a question of convenience,
>
> I am looking to sum the values of one column based on another column - a example may help explain better!
>
> ED ECOCODE
> 21.809467 AA0101
> 36.229566 PA1201
> 51.861284 PA1201
> 11.36232 PA1201
> 27.264634 PA1201
> 12.261986 PA1201
> 46.519313 PA1201
> 7.815376 PA1201
> 2.810428 PA1201
> 13.478372 PA1201
> 35.670182 PA1301
> 27.128715 AT0801
> 19.010294 AT1201
> 15.475368 AT1201
> 18.597983 AT0101
> 29.292615 AT0101
> 6.749846 AT0101
> 14.981488 AT0101
> 14.93511 AT0101
> 14.93511 AT0101
> 21.040785 AT0101
> 8.271615 AT0101
> 12.94232 AT0101
> 6.749846 AT0101
> 15.484412 AT0101
> 29.644494 AT0101
> 43.211212 AT0101
>
> So for AA0101 it would be = 21.809467
> AT1201 it would be = 19.010294+15.475368
>
> etc
>
> I would then like to be able to output a table with ECOCODE in one column and the sum of ED in the other.
>
> This is stored in a dataframe called ecoregion, i understand people like having code to change but i have none as i am a relative beginner! Sorry in advance!
>
> Thanks
>
> Peter
>
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David Winsemius, MD
West Hartford, CT
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