[R] Plot Arrows with Angle and length - correction

[S Ellison]

Apologies; 'length' is an arrows() argument. Use something else - see below.

> > x<- c(1,2,4)
> > y<- c(2,3,5)
> > Azimuth<- c(45,90,180)
> > Length<- c(1,0.5,1)

May be packages out there but if it's a quick fix you want, roll your own.

arrows.az <- function(x, y, azimuth, size, ..., units=c("degrees", "radians")) {
	#Using 'size' to avoid clash with arrows(..., length=...)
	units <- match.arg(units)
	az.rad <- switch(units,
		degrees=azimuth*pi/180,
		radians=azimuth
	)
	arrows(x, y, x+cos(az.rad)*size, y+sin(az.rad)*size, ...)
}

plot(0:6, 0:6, type="n")
arrows.az(x, y, Azimuth, Length)

"..." means you can pass all the other options to arrows()

S Ellison


> 
> 
> Thanks,
> 
> Julio
> 
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> 
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