[R] Performing stats on group of observations

[Bert Gunter]

"... trying to figure it out" ??

Not sure what that means.Have you read "An Introduction to R."? If
not, do so now.

In any case, ?ave is made for what you want, I think (simpler than
?by). As in (if df is your data frame):

ave(df$NoFlights,df$Week, FUN= mean)

Or, better yet, using ?with and noting that mean is the default for FUN

with(df,ave(NoFlights,Week))

Cheers,
Bert




On Mon, Jun 24, 2013 at 4:53 PM, Ion Mateescu <ion.matees at gmail.com> wrote:
> This may be a simple problem but I spent most of my day today trying to
> figure it out, as I am not a programmer. I have a dataframe with
> observations from different weeks of the year, numbered. My variable
> "week" has values week1, week4, week9, etc. Not all weeks are represented.
> I need to calculate statistics and compare means for a measured variable
> (no_of_flights) :
>
> Week    NoFlights
> week1    31.00
> week1    31.00
> week1    36.00
> week1    32.00
> week1    30.00
> week1    30.00
> week1    30.00
> week2    31.00
> week2    32.00
> week1    30.00
> week1    31.00
> week1    32.00
> week23    30.00
> week23    35.00
> week57    30.00
> week1    32.00
> week1    33.00
> week1    33.00
> week2    30.00
> week2    33.00
> week1    32.00
> week1    32.00
> week1    33.00
> week23    28.00
>
> Any help is appreciated.
>
> River
>
>         [[alternative HTML version deleted]]
>
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-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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