[R] How to Calculate the Mean by Multiple Groups in R
Sarah Goslee
@@r@h@go@|ee @end|ng |rom gm@||@com
Tue Oct 24 14:40:46 CEST 2023
Hi,
I think you're misunderstanding which set of variables go on either
side of the formula.
Is this what you're looking for?
> aggregate(OD ~ Time + Target + Conc, data = df, FUN = "mean")
Time Target Conc OD
1 1 BACT 1 765.3333
2 1 BACT 2 745.3333
3 1 BACT 3 675.0000
> aggregate(ODnorm ~ Time + Target + Conc, data = df, FUN = "mean")
Time Target Conc ODnorm
1 1 BACT 1 108.33333
2 1 BACT 2 88.33333
3 1 BACT 3 18.00000
Or using a different form, that might be more straightforward to you:
> aggregate(df[, c("OD", "ODnorm")], by = df[, c("Time", "Target", "Conc")], data = df, FUN = "mean")
Time Target Conc OD ODnorm
1 1 BACT 1 765.3333 108.33333
2 1 BACT 2 745.3333 88.33333
3 1 BACT 3 675.0000 18.00000
Sarah
On Tue, Oct 24, 2023 at 8:31 AM Luigi Marongiu <marongiu.luigi using gmail.com> wrote:
>
> Hello,
> I have a data frame with different groups (Time, Target, Conc) and
> each entry has a triplicate value of the measurements OD and ODnorm.
> How can I merge the triplicates into a single mean value?
> I tried the following:
> ```
> df = data.frame(Time=rep(1, 9), Well=paste("A", 1:9, sep=""),
> OD=c(666, 815, 815, 702, 739, 795, 657, 705, 663),
> Target=rep("BACT", 9),
> Conc=c(1,1,1,2,2,2,3,3,3),
> ODnorm=c(9, 158, 158, 45, 82, 138, 0, 48, 6),
> stringsAsFactors = FALSE)
> aggregate(.~ODnorm, df, mean)
>
> > aggregate(.~ODnorm, df, mean)
> ODnorm Time Well OD Target Conc
> 1 0 NA NA NA NA NA
> 2 6 NA NA NA NA NA
> 3 9 NA NA NA NA NA
> 4 45 NA NA NA NA NA
> 5 48 NA NA NA NA NA
> 6 82 NA NA NA NA NA
> 7 138 NA NA NA NA NA
> 8 158 NA NA NA NA NA
>
> aggregate(cbind(Time, Target, Conc) ~ ODnorm, df, mean)
> ODnorm Time Target Conc
> 1 0 NA NA NA
> 2 6 NA NA NA
> 3 9 NA NA NA
> 4 45 NA NA NA
> 5 48 NA NA NA
> 6 82 NA NA NA
> 7 138 NA NA NA
> 8 158 NA NA NA
> ```
>
> Thank you.
>
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--
Sarah Goslee (she/her)
http://www.numberwright.com
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