Created
February 17, 2017 23:16
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Mean direction and mean strength of wind by vector addition
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| # circular means by using vector method #### | |
| # from http://math.stackexchange.com/questions/44621/calculate-average-wind-direction | |
| circmean <- function(ws,wd,na.rm=TRUE) { | |
| V_east = mean(ws*sin(wd * pi/180),na.rm=na.rm) | |
| V_north = mean(ws*cos(wd * pi/180),na.rm=na.rm) | |
| mean_WD = atan2(V_east, V_north) * 180/pi | |
| mean_WD = (360 + mean_WD) %% 360 | |
| return(mean_WD) | |
| } | |
| circlength <- function(ws,wd,na.rm=TRUE) { | |
| V_east = mean(ws*sin(wd * pi/180),na.rm=na.rm) | |
| V_north = mean(ws*cos(wd * pi/180),na.rm=na.rm) | |
| mean_WS = sqrt(V_east^2+V_north^2) | |
| return(mean_WS) | |
| } |
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Input
ws = vector = wind speed (any units)
wd = vector = wind direction (0-359 degrees)
Output:
scalar mean wind direction (0-359 degrees), mean wind speed