I have a data frame like this: Expt Replicate A 1 A 2 A

Question

Asked: June 7, 20262026-06-07T18:34:05+00:00 2026-06-07T18:34:05+00:00

I have a data frame like this:

Expt    Replicate
A       1
A       2
A       3
B       1
B       2
B       3
C       1
C       2
C       3
C       4

I want to return the number of replicates for each experiment. Like this:

Expt    #Reps
A       3
B       3
C       4

This has got to be super simple, but I have tried some things like

ddply(df, Expt, .fun=max(Replicate))

with no luck. Please help.

You must login to add an answer.

Need An Account,

Editorial Team · Answer 1 · 2026-06-07T18:34:07+00:00

Editorial Team

another simple way:

 summary(df[,1]) #where df is your data frame and you want the 1st column counts ("Expt")

Note: the 1st column is a factor and this applies to any columns which are factor

The Archive Base Latest Questions