pro draw_circle,centre,radius,noerase=noerase, $
axes=axes,color=color,a_color=a_color,linestyle=linestyle, $
a_linestyle=a_linestyle,thick=thick

;	Draws a circle of a given radius and centre.

if n_elements(noerase) le 0 then noerase=0
if n_elements(color) le 0 then color=!p.color
if n_elements(thick) le 0 then thick=1
if n_elements(a_color) le 0 then a_color=!p.color
if n_elements(linestyle) le 0 then linestyle=!p.linestyle
if n_elements(a_linestyle) le 0 then a_linestyle=!p.linestyle

N=(!d.x_vsize < !d.x_vsize)/2
t=findgen(N)*(!pi*2/(N-1))
x=sin(t)
y=cos(t)
x0=float(centre(0)-radius)/!d.x_vsize
x1=float(centre(0)+radius)/!d.x_vsize
y0=float(centre(1)-radius)/!d.y_vsize
y1=float(centre(1)+radius)/!d.y_vsize
;plot,x,y,xst=5,yst=5,pos=[x0,y0,x1,y1]*0.9999,noerase=noerase, $
;	color=color,linestyle=linestyle,thick=thick

plots,x*radius+centre(0),y*radius+centre(1),color=color,linestyle=linestyle,thick=thick,/dev;,noerase=noerase



	if keyword_set(axes) then begin
xc=float(centre(0))/!d.x_vsize
yc=float(centre(1))/!d.y_vsize
plots,[xc,xc],[0,1],/nor,color=a_color,linestyle=a_linestyle
plots,[0,1],[yc,yc],/nor,color=a_color,linestyle=a_linestyle

	endif

end