import PyArt,whrandom, math

w = 356
h = w* (2/3.0)  # width and height of canvas

canvas = PyArt.Canvas(w,h, bg=0x7f7f7f)

# set up coordinate system so it start in lower left hand corner and y increases
# upwards
canvas.translate(0,h)
canvas.scale(1,-1)



canvas.gsave()

#x0, y0 = 85.3333, 85.3333  # let this be the origin of the graph
x0, y0 = .20*w, .25*h  # let this be the origin of the graph

canvas.translate(x0,y0) # move to origin of graph

# define paths for x and y axes
yaxis = PyArt.Path()

y_range = h-2*y0 # for now
yaxis.moveto_open(0,0)
yaxis.lineto(0, y_range)
yaxis.end()

x_range = w - 2*x0
xaxis = PyArt.Path()
xaxis.moveto_open(0,0)
xaxis.lineto(x_range,0)
xaxis.end()

canvas.gstate.stroke= 0x000000
canvas.stroke(yaxis)

canvas.stroke(xaxis)

# draw x-axis label
canvas.gstate.font_size = 16 # ~16 pixels high
canvas.gsave()
canvas.translate(x_range/2.0-15, -20) # need to subtract off 1/2 width of string

canvas.gstate.fill = 0x000000
canvas.drawString(0,0, "time", flipY=0)
canvas.grestore()

# y-axis label
canvas.gsave()
canvas.translate(-20, y_range/2.0 - 25)
canvas.rotate(-90)
canvas.gstate.fill = 0x000000
canvas.drawString(0,0,"response", flipY=0)
canvas.grestore()




canvas.translate(5,5)
# plot a random line with a small quadratic dependence
print "Generating data"
# cover most of x range
x_end = x_range*.95
y_end = y_range*.87
totpt = 50
xs = x_end/totpt
ys = y_end/x_end

data = PyArt.Path(totpt+2)
data.moveto_open(0.0,0.0)

for ii in range(totpt):
    x = ii * xs
    delta = whrandom.random() * y_range
    y = (0.5)*ys * x + 0.5*delta  + 15* math.sin(.04*x) # y = linear + sin + random
    #print x,y
    data.lineto(x,y)


data.end()
canvas.gstate.stroke_width = 1.2

canvas.gstate.stroke = 0x00FF7f
canvas.gstate.stroke_opacity = 1.0
canvas.stroke(data)


canvas.save("demo2.png")