[R] Sum with condition

[S Ellison]

If you used aggregate() on  the data frame you would have a new data frame containing the sum of all AreaProtected for each CELLCD. For your mini-example, using d as your data frame, 
d2<-aggregate(d[,2], by=list(CELLCD=d$CELLCD),sum)

d2
#   CELLCD        x
# 1   8928 94.30900
# 2   8929 84.87900
# 3   8930 40.13149

If you then use merge() you get
merge(d,d2)

#  CELLCD AreaProtected        x
#1   8928      52.39389 94.30900
#2   8928      41.91511 94.30900
#3   8929      21.21975 84.87900
#4   8929      63.65925 84.87900
#5   8930      26.08547 40.13149
#6   8930      14.04602 40.13149

Maybe one of those is what you want?


> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Celine
> Sent: 02 November 2011 12:44
> To: r-help at r-project.org
> Subject: [R] Sum with condition
> 
> I guess my problem is simple for most of you but I am new 
> with R and I need some help, I have a dataframe : 
> 
> CELLCD AreaProtected
>    8928      52.39389
>    8928      41.91511
>    8929      21.21975
>    8929      63.65925
>    8930      26.08547
>    8930      14.04602
> 
> I wouldlike to sum the AreaProtected if it is the same CELLCD 
> in another column :
> 
> CELLCD AreaProtected    SumAreaProtected
>    8928      52.39389      94.309
>    8928      41.91511
>    8929      21.21975      84,879
>    8929      63.65925
>    8930      26.08547
>    8930      14.04602
> 
> I am just started with R and I don't know how I can do that.
> Do you have any ideas ?
> 
> 
> Thanks a lot for your help,
> 
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