R help - May 2023 - aggregate wind direction data with wind speed required

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 at regione.marche.it
---Oo---------oO----------------------------------------

________________________________

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?s 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 at 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 at 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

I think that using complex numbers to represent the wind velocity makes
this simpler.  You would need to write some simple conversion functions
since wind directions are typically measured clockwise from north and the
argument of a complex number is measured counterclockwise from east.  E.g.,

windToComplex <-
function(speed, degreesCW) {
  complex(mod=speed, arg=(90-degreesCW)/180*pi)
}
complexToWind <-
function(z) {
  # Convert complex velocity z to speed and direction (degrees clockwise
  # from north, in range [0,360)).
  stopifnot(is.complex(z))
  data.frame(speed = Mod(z), degreesCW = (pi - Arg(z*1i))/(2*pi)*360)
}

Then use FUN=mean instead of my_fun.

-Bill

On Sat, May 13, 2023 at 7:51?AM Stefano Sofia <
stefano.sofia at regione.marche.it> wrote:
> 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 at 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 at 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.
>
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