!ELLIPSE
!This macro creates keypoints on one of the upper quadrants of an ellipse
!given the following parameters, and stores the coordinates in XS an YS:

a=arg1	!minor radius of ellipse
b=arg2	!major radius of ellipse
x0=arg3	!x-coordinate of centre of ellipse
y0=arg4 !y-coordinate of centre of ellipse
n=arg5	!number of segments
f=arg6  !f=-1 ==> left quadrant, f=1 ==> right quadrant


XS=
YS=

*DIM,XS,ARRAY,N+1
*DIM,YS,ARRAY,N+1

dx=a/N

*DO,i,1,N+1
x=(i-1)*dx
x=x*f
xs(i)=x+x0
ys(i)=sqrt((1-(x/a)**2)*b**2)+y0
K,,xs(i),ys(i)
*enddo