[R] aggregate wind direction data with wind speed required

[Stefano Sofia]

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)
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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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