CODEWITHSUNDEEP
r
KS Lee
KS Lee

Reputation: 91

How can I calculate wind direction average in R?

I have a data set which consist of wind direction vector, as follows:

wdir <- c(296.9, 215.2, 204.8, 110.8, 287.6, 203.4, 253.1, 46.0, 298.8,  62.8, 183.4, 62.3,
          44.3, 97.6, 78.6, 125.6, 116.9, 121.0, 111.2, 335.8, 287.4, 51.7, 232.6, 265.5,
          269.7, 20.5, 17.0, 310.8)

Scalar values are in degrees.

How can I calculate mean wind direction?

Upvotes: 6

Views: 5421

Answers (2)

Alessio Golzio
Alessio Golzio

Reputation: 41

You can't simply average the wind direction, you need the speed for each direction and with the speed you can evaluate the average considering the vector form. Another way is to convert wind speed and direction into u and v components, than you can average u and v separately and then evaluating speed and direction. Wind spd = sqrt(u^2+v^2); wind dir = atan2(u,v)*(180/pi)+180

Upvotes: 4

germcd
germcd

Reputation: 944

This can be done using the circular package.

To get the mean of 45 and 315 you can use:

library(circular)
mean(circular(c(pi/4,7*pi/4)))
#Circular Data: 
#Type = angles 
#Units = radians 
#Template = none 
#Modulo = asis 
#Zero = 0 
#Rotation = counter 
#[1] -1.570092e-16

The reason it isn't exactly 0 is because of floating point precision in R.

To get the mean of wdiryou can use:

mean(circular(wdir, units = "degrees"))
#Circular Data: 
#Type = angles 
#Units = degrees 
#Template = none 
#Modulo = asis 
#Zero = 0 
#Rotation = counter 
#[1] 41.05411

Another example:

mean(circular(c(7*pi/2,pi/4, pi/2, 7*pi/2 )))
#Circular Data: 
#Type = angles 
#Units = radians 
#Template = none 
#Modulo = asis 
#Zero = 0 
#Rotation = counter 
#[1] -0.3926991

Upvotes: 10

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