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plot an angle of 450 degrees and adding a circular arrow to it

6 messages · Albyn Jones, Steven Stoline, Joel Schwartz

Original
Steven Stoline
# 
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
Albyn Jones
# 
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:

            

      
      
      
    

        

      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Steven Stoline
    

    

      
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Many thanks

it works

Steven

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

        

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

  
    

      
      
    

  


  


      

    

    
1 day later

    

      
      

        


  

        

      Steven Stoline
    

    

      
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Dear Jones:

Could you please look to this R code. I am trying to graph both sin(x+pi/6)
and sin(x) in the same plot to show the shift. I used abline to graph the
sin(x), but it looked like same as the x-axis.


x<-seq(-2.2*pi,2*pi,0.01)
y<-sin(x+pi/6)


#### To draw a box of the graph:
#### ==========================

plot(0:10, 0:10, type = "n", xaxt = "n", yaxs = "i", xaxs = "i", yaxt =
"n", xlab = "", ylab = "")

plot(x, y, type='l', lwd = 3,  col="red", xaxt = "n", xlab="", ylab="")



#### abline(v=c(-4*pi,-(7*pi)/2,-3*pi,-(5*pi)/2,-2*pi,-(3*pi)/2,-pi,-pi/2,
0,pi/2,pi,(3*pi)/2,2*pi,(5*pi)/2,3*pi,(7*pi)/2,4*pi),col="blue")


abline(h=0, lwd=3)
abline(v=0, lwd=3)


x1<-seq(0,2*pi,0.01)
y1<-sin(x1)
abline(x1,y1, lwd = 3)


thank you very much
Steven

        
On Mon, Oct 20, 2014 at 1:08 PM, Steven Stoline <sstoline at gmail.com> wrote:

        

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Albyn Jones
    

    

      
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you want the lines() function, not abline()

albyn

        
On Tue, Oct 21, 2014 at 11:30 AM, Steven Stoline <sstoline at gmail.com> wrote:

        

            

      
      
      
    

        

      
      
    

            

      
      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Joel Schwartz
    

    

      
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Steven,

Change

abline(x1,y1, lwd = 3) to lines(x1,y1, lwd = 3) and you'll get the line you're looking for. abline is just for drawing a line with a given slope and intercept. lines is more general.

Also, c(-4*pi,-(7*pi)/2,-3*pi,-(5*pi)/2,-2*pi,-(3*pi)/2,-pi,-pi/2, 0,pi/2,pi,(3*pi)/2,2*pi,(5*pi)/2,3*pi,(7*pi)/2,4*pi)
can be done with a call to seq instead. For example:
seq(-4*pi, 4*pi, pi/2)

Best Wishes,
Joel

        
On Oct 21, 2014, at 11:30 AM, Steven Stoline <sstoline at gmail.com> wrote: