[R] aggregate wind direction data with wind speed required

[Bert Gunter]

Sorry Rui; if you run your code you will get:
Error in FUN(X[[i]], ...) : object 'ws' not found

Moreover, even if you did this:
aggregate(wd ~ day + month, data=df, FUN = my_fun, ws1 = df$ws)
 the answer would be wrong is you need to include only the subsets of ws1
corresponding to the split defined by day + month in each call to my_fun.
aggregate() does not do this (the ... argument is evaluated only once, not
once per subset).

So I think the answer to Stefano's question is no, aggregate doesn't work.
You should use by() or tapply() instead:

##Warning: I haven't checked this carefully. So please do!

>  by(df, list(df$day,df$month), FUN = \(x)with(x, my_fun(wd, ws)))

Cheers,
Bert



On Sat, May 13, 2023 at 8:54 AM Rui Barradas <ruipbarradas using sapo.pt> wrote:

> Às 15:51 de 13/05/2023, Stefano Sofia escreveu:
> > Dear list users,
> >
> > I have to aggregate wind direction data (wd) using a function that
> requires also a second input variable, wind speed (ws).
> >
> > This is the function that I need to use:
> >
> >
> > my_fun <- function(wd1, ws1){
> >
> >    u_component <- -ws1*sin(2*pi*wd1/360)
> >    v_component <- -ws1*cos(2*pi*wd1/360)
> >    mean_u <- mean(u_component, na.rm=T)
> >    mean_v <- mean(v_component, na.rm=T)
> >    mean_wd <- (atan2(mean_u, mean_v) * 360/2/pi) + 180
> >    result <- mean_wd
> >    result
> > }
> >
> > Does the aggregate function work only with functions with a single input
> variable (the one that I want to aggregate), or its use can be extended to
> functions with two input variables?
> >
> > Here a simple example (which is meaningless, the important think is the
> concept behind it):
> > df <- data.frame(day=c(1, 1, 1, 2, 2, 2, 3, 3), month=c(1, 1, 2, 2, 2,
> 2, 2, 2), wd=c(45, 90, 90, 135, 180, 270, 270, 315), ws=c(7, 7, 8, 3, 2, 7,
> 14, 13))
> >
> > aggregate(wd ~ day + month, data=df, FUN = my_fun)
> >
> > cannot work, because ws is not taken into consideration.
> >
> > I got lost. Any hint, any help?
> > I hope to have been able to explain my problem.
> > Thank you for your attention,
> > Stefano
> >
> >
> >           (oo)
> > --oOO--( )--OOo--------------------------------------
> > Stefano Sofia PhD
> > Civil Protection - Marche Region - Italy
> > Meteo Section
> > Snow Section
> > Via del Colle Ameno 5
> > 60126 Torrette di Ancona, Ancona (AN)
> > Uff: +39 071 806 7743
> > E-mail: stefano.sofia using regione.marche.it
> > ---Oo---------oO----------------------------------------
> >
> > ________________________________
> >
> > AVVISO IMPORTANTE: Questo messaggio di posta elettronica pu� contenere
> informazioni confidenziali, pertanto � destinato solo a persone autorizzate
> alla ricezione. I messaggi di posta elettronica per i client di Regione
> Marche possono contenere informazioni confidenziali e con privilegi legali.
> Se non si � il destinatario specificato, non leggere, copiare, inoltrare o
> archiviare questo messaggio. Se si � ricevuto questo messaggio per errore,
> inoltrarlo al mittente ed eliminarlo completamente dal sistema del proprio
> computer. Ai sensi dell'art. 6 della DGR n. 1394/2008 si segnala che, in
> caso di necessit� ed urgenza, la risposta al presente messaggio di posta
> elettronica pu� essere visionata da persone estranee al destinatario.
> > IMPORTANT NOTICE: This e-mail message is intended to be received only by
> persons entitled to receive the confidential information it may contain.
> E-mail messages to clients of Regione Marche may contain information that
> is confidential and legally privileged. Please do not read, copy, forward,
> or store this message unless you are an intended recipient of it. If you
> have received this message in error, please forward it to the sender and
> delete it completely from your computer system.
> >
> > --
> >
> > Questo messaggio  stato analizzato da Libraesva ESG ed  risultato non
> infetto.
> >
> > This message was scanned by Libraesva ESG and is believed to be clean.
> >
> >
> >       [[alternative HTML version deleted]]
> >
> >
> > ______________________________________________
> > R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> Hello,
>
> Use the dots argument to pass any number of named arguments to your
> aggregation function.
> In this case, ws1 = ws at the end of the aggregate call.
>
>
> aggregate(wd ~ day + month, data=df, FUN = my_fun, ws1 = ws)
>
>
> You can also give the user the option to remove or not NA's by adding a
> na.rm argument:
>
>
> my_fun <- function(wd1, ws1, na.rm = FALSE) {
>    [...]
>    mean_u <- mean(u_component, na.rm = na.rm)
>    mean_v <- mean(v_component, na.rm = na.rm)
>    [...]
> }
>
> aggregate(wd ~ day + month, data=df, FUN = my_fun, ws1 = ws, na.rm = TRUE)
>
>
> Hope this helps,
>
> Rui Barradas
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

	[[alternative HTML version deleted]]