[R] How to Calculate the Mean by Multiple Groups in R
Luigi Marongiu
m@rong|u@|u|g| @end|ng |rom gm@||@com
Tue Oct 24 14:31:11 CEST 2023
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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