use 'math'
local function star(r)
 local a, ae = 54*pi/180, 72*pi/180
 local li, hi = r*cos(a), r*sin(a)
 local he = li*tan(ae)
 local xv, yv = 0, - hi - he
 local xb, yb = - li, - hi
 local p = graph.path(xv, yv)
 p:line_to(xb, yb)
 for k=1, 4 do
 local th = 2*pi*k/5
 p:line_to(xv*cos(th) + yv*sin(th), yv*cos(th) - xv*sin(th))
 p:line_to(xb*cos(th) + yb*sin(th), yb*cos(th) - xb*sin(th))
 end
 p:close()
 return p
end
local function demo1()
 local plt = graph.canvas 'rotating star'
 plt.units = false
 plt:show()
 local a = 15.0
 plt:limits(-a, -a, a, a)
 local r = rng.new()
 local gray1, gray2 = graph.rgb(230, 230, 230), graph.rgb(155, 155, 155)
 for k = 1, 50 do
 local x, y = (2*r:get()-1)*a, (2*r:get()-1)*a
 local d = rnd.gaussian(r, 0.015*a) + 0.03*a
 local s = star(d)
 plt:add(s, gray1, {}, {{'translate', x=x, y=y}})
 plt:addline(s, gray2, {}, {{'translate', x=x, y=y}})
 end
 plt:pushlayer()
 local N, R, nc = 128, 5.0, 8
 local yellow, dark = graph.rgba(255, 255, 0, 180), graph.rgb(128, 128, 0)
 for k = 0, N * nc do
 local r = R * cos(pi*k/N)^2
 local th = 2*pi*(k/(N*nc*10))
 local s= star(r)
 plt:clear()
 plt:add(s, yellow, {}, {{'rotate', angle=th}})
 plt:addline(s, dark, {}, {{'rotate', angle=th}})
 plt:flush()
 end
end
local function demo2()
 local f = |x| exp(-0.1*x) * cos(x)
 local p = graph.plot 'y = f(x)'
 local x0, x1 = 0, 10*pi
 local cc = graph.fxline(f, x0, x1, k)
 p.sync = false
 p:limits(0, -1, 10*pi, 1)
 p:pushlayer()
 p:show()
 local N = 256
 local yellow = graph.rgba(255,255,0,155)
 for k= 2, N do
 local x = x0 + k * (x1-x0) / N
 local ca = graph.fxline(f, x0, x, k)
 ca:line_to(x, 0); ca:line_to(0, 0); ca:close()
 p:clear()
 p:add(ca, yellow)
 p:addline(cc)
 p:flush()
 end
end
local function demo3()
 local p = graph.plot 'box plot'
 local r = rng.new()
 r:set(os.time())
 p:addline(graph.rect(-10, -10, 10, 10), 'blue', {{'dash', 7, 3}})
 p.sync = false
 p:pushlayer()
 p:show()
 
 local L = 100
 local get = || rnd.gaussian(r, L/2)
 local N = 256
 for k=1, N do
 p:clear()
 for j=1, 4 do
	 local x, y, rad = get(), get(), 5 + r:get() * L/2
	 local rt = graph.circle(x, y, rad)
	 p:add(rt, graph.rgba(r:getint(255), r:getint(255),r:getint(255), 128))
	 p:addline(rt, 'black')
 end
 p:flush()
 end
 return p
end
return {'Animations', {
 {
 name = 'anim1',
 f = demo1, 
 description = 'Rotating Star'
 },
 {
 name = 'anim2',
 f = demo2, 
 description = 'Function\'s definite integral illustation'
 },
 {
 name = 'anim3',
 f = demo3, 
 description = 'Animation stress test with automatic plot limits'
 },
}}
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