[Matplotlib-users] Line update: set_data vs recache issue

[Antonino I. <tri...@gm...>]

Hi to all,

I'm doing a simple animation like this:

--
ion()
x = arange(0,2,0.01)
y = zeros_like(x)
y[45:55]=1
l, = plot(x,y)

D = 0.1
h = x[1]-x[0]
dt = 0.0001;

def nabla(v,h):
    na = zeros_like(v)
    na[1:-1] = (v[2:]-2*v[1:-1]+v[:-2])
    na[0],na[-1] = 0,0
    return na/(h**2)

for i in range(1000):
    y = y + D*nabla(y,h)*dt
    if i%10 == 0:
        l.set_ydata(y)
        draw()
--

however, changing the line

    y = y + D*nabla(y,h)*dt with

in

    y += D*nabla(y,h)*dt

the plot is not updated anymore. I have to replace l.set_ydata(y) with
y.recache() to make the the animation work again.

I think this is a bug since the line should be updated even using the
+= operator.

Regards,
Antonio