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Sorry I am not experienced in R, but the code is probably very simple. I have a big dataset of which I want to calculate the SD for each sample per group. Here is an example;

Measurement     Sample      Group
50              1           minimum
60              1           minimum
80              1           minimum
300             1           maximum
400             1           maximum
350             1           maximum
70              2           minimum
80              2           minimum
100             2           minimum
4000            2           maximum
4200            2           maximum
3500            2           maximum

and what I expect as an outcome;

SD      Sample      Group
value   1           minimum
value   1           maximum
value   2           minimum
value   2           maximum

Thanks in advance!

Jesse
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  • Could you add what has failed? – NelsonGon Apr 24 '20 at 13:58
  • This is a summary-by-group using the `sd` function. Some options are `aggregate(Measurement ~ Sample + Group, data = df, FUN = sd)` or `library(dplyr); df %>% group_by(Sample, Group) %>% summarise(stdev = sd(Measurement))` or `library(data.table); setDT(df); df[, .(stdev = sd(Measurement)), by = .(Sample, Group)]` – IceCreamToucan Apr 24 '20 at 14:00

0 Answers0