[R] aggregate wind direction data with wind speed required

[Rui Barradas]

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
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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