[R-sig-teaching] plot an angle of 450 degrees and adding a circular arrow to it

[Steven Stoline]

Many thanks

it works

Steven

On Mon, Oct 20, 2014 at 11:17 AM, Albyn Jones <jones at reed.edu> wrote:

> Here is a quickly written and barely tested function.  You might want to
> add a final position vector,
> color, lwd, lty, etc.  It assumes the angle is given in degrees, and
> checks the sign of the angle to draw
> in the correct direction.
>
> albyn
> =====================================================================
>
> DrawAngle  <- function(theta,r=1){
>     # assumes angles given in degrees, not radians
>     theta <- 2*pi*theta/360
>     plot(0,0, xlim=c(-2,2),ylim=c(-2,2))
>     abline(h=0)
>     abline(v=0)
>     sgn <- 1
>     if(theta <0) {
>         sgn  <- -1
>         theta <- -theta
>         }
>     Theta <-  sgn*seq(0,theta,.01)
>     if(theta > 2*pi) r <- seq(1,1.1,along.with=Theta)
>     x <- r*cos(Theta)
>     y <- r*sin(Theta)
>     lines(x,y)
>     n <- length(x)
>     arrows(x[n-1],y[n-1],x[n],y[n])
> }
>
> On Mon, Oct 20, 2014 at 1:47 AM, Steven Stoline <sstoline at gmail.com>
> wrote:
>
>> Dear All:
>>
>> I am wondering if someone can show me how to plot an angles around the
>> center of a unit circle with x-y vertices added to it.
>>
>> Also how to add arrows showing the size and the direction of angle(s).
>>
>> Examples: 135 degrees and 450 degrees angles.
>>
>> with many thanks
>> Steven
>>
>> --
>> Steven M. Stoline
>> 1123 Forest Avenue
>> Portland, ME 04112
>> sstoline at gmail.com
>>
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>>
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>>
>
>


-- 
Steven M. Stoline
1123 Forest Avenue
Portland, ME 04112
sstoline at gmail.com

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