[R] Sum by column

[Felipe Carrillo]

Or with ddply :
library(plyr)
dat <- structure(list(ED = c(21.809467, 36.229566, 51.861284, 11.36232,
27.264634, 12.261986, 46.519313, 7.815376, 2.810428, 13.478372,
35.670182, 27.128715, 19.010294, 15.475368, 18.597983, 29.292615,
6.749846, 14.981488, 14.93511, 14.93511, 21.040785, 8.271615,
12.94232, 6.749846, 15.484412, 29.644494, 43.211212), ECOCODE = structure(c(1L,
5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 6L, 3L, 4L, 4L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("AA0101",
"AT0101", "AT0801", "AT1201", "PA1201", "PA1301"), class = "factor")),
.Names = c("ED",
"ECOCODE"), class = "data.frame", row.names = c(NA, -27L))
dat
ddply(dat,"ECOCODE",summarise,EDsummed=sum(ED))
 
Felipe D. Carrillo
Supervisory Fishery Biologist
Department of the Interior
US Fish & Wildlife Service
California, USA
http://www.fws.gov/redbluff/rbdd_jsmp.aspx




----- Original Message ----
> From: Peter Francis <peterfrancis at me.com>
> To: r-help at r-project.org
> Sent: Wed, January 12, 2011 2:38:19 AM
> Subject: [R] Sum by column
> 
> 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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