Hello Group,
I need a modification in the data.table example to get my intended
result shown below ... is there a more simple way!
dt <- data.table(A = rep(1:3, each=4), B = rep(1:4, each=3), C = rep(1:2, 6))
dt[, transform(.SD,D=mean(A)), by="B"]
The result I want is below ... which is probably long winded!
data.table(unique(as.data.frame(dt[, transform(.SD,D=mean(A)),
by="B"][,list(B,D)])))
B D
[1,] 1 1.000000
[2,] 2 1.666667
[3,] 3 2.333333
[4,] 4 3.000000
Thank you.
On Fri, Dec 3, 2010 at 6:38 PM, Santosh Srinivas <santosh.srinivas at gmail.com> wrote:> Hello Group, > > I need a modification in the data.table example to get my intended > result shown below ... is there a more simple way! > > dt <- data.table(A = rep(1:3, each=4), B = rep(1:4, each=3), C = rep(1:2, 6)) > dt[, transform(.SD,D=mean(A)), by="B"] > > > The result I want is below ... which is probably long winded! > > data.table(unique(as.data.frame(dt[, transform(.SD,D=mean(A)), > by="B"][,list(B,D)]))) > ? ? B ? ? ? ?D > [1,] 1 1.000000 > [2,] 2 1.666667 > [3,] 3 2.333333 > [4,] 4 3.000000 >data.table has its own mailing list. -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com
Hi:
dt[, mean(A), by = 'B']
B V1
[1,] 1 1.000000
[2,] 2 1.666667
[3,] 3 2.333333
[4,] 4 3.000000
...and I can see you've found the data.table mailing list...
HTH,
Dennis
On Fri, Dec 3, 2010 at 3:38 PM, Santosh Srinivas
<santosh.srinivas@gmail.com> wrote:
> Hello Group,
>
> I need a modification in the data.table example to get my intended
> result shown below ... is there a more simple way!
>
> dt <- data.table(A = rep(1:3, each=4), B = rep(1:4, each=3), C =
rep(1:2,
> 6))
> dt[, transform(.SD,D=mean(A)), by="B"]
>
>
> The result I want is below ... which is probably long winded!
>
> data.table(unique(as.data.frame(dt[, transform(.SD,D=mean(A)),
> by="B"][,list(B,D)])))
> B D
> [1,] 1 1.000000
> [2,] 2 1.666667
> [3,] 3 2.333333
> [4,] 4 3.000000
>
> Thank you.
>
> ______________________________________________
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>
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