How to Calculate the Mean by Multiple Groups in R
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 at 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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