program anim_circ_xy implicit none real r,rold,theta,d_theta, x,y,xold,yold integer i, idummy, pgopen idummy = pgopen('/xwin') call pgenv(-5.0,5.0,-5.0,5.0,1,0) call pgsfs(2) r=2.0 xold=0.0 yold=0.0 call pgcirc(xold,yold,r) rold=2.0 d_theta=2*3.14159/3600 theta=0 x=0.0 do i=1,1000000 theta = theta + d_theta r = 1.0 + 0.3*sin(0.2*theta) x = 0.8*sin(theta) y = 0.0 call pgbbuf call pgsci(0) call pgcirc(xold,yold,rold) call pgsci(1) call pgcirc(x,y,r) call pgebuf rold=r xold=x yold=y end do call pgclos end