Bar-plot animation using matplotlib

Question

I am trying to plot the animation of bar plots updating their values in colab using matplotlib animations.

def barlist(n): 
     return val[n]

fig=plt.figure()

n=100 #Number of frames
x=range(16)
barcollection = plt.bar(x, barlist(0))

def animate(i):
    y = barlist(i+1)
    for i, b in enumerate(barcollection):
        b.set_height(y[i])

anim=animation.FuncAnimation(fig,animate,blit=False,repeat=False,frames=100, interval=10)

anim.save('movie.mp4',writer=animation.FFMpegWriter(fps=10))

Here is sample of first 5 of 142 values of val array. The range of y values is 0 to -25 and the range of x values range from 0 to 15.

[array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0.]),
 array([ 0.       , -1.       , -1.25     , -1.3125   , -1.       ,
        -1.5      , -1.6875   , -1.75     , -1.25     , -1.6875   ,
        -1.84375  , -1.8984375, -1.3125   , -1.75     , -1.8984375,
         0.       ]),
 array([ 0.        , -1.9375    , -2.546875  , -2.73046875, -1.9375    ,
        -2.8125    , -3.23828125, -3.40429688, -2.546875  , -3.23828125,
        -3.56835938, -3.21777344, -2.73046875, -3.40429688, -3.21777344,
         0.        ]),
 array([ 0.        , -2.82421875, -3.83496094, -4.17504883, -2.82421875,
        -4.03125   , -4.7097168 , -4.87670898, -3.83496094, -4.7097168 ,
        -4.96374512, -4.26455688, -4.17504883, -4.87670898, -4.26455688,
         0.        ]),
 array([ 0.        , -3.67260742, -5.0980835 , -5.58122253, -3.67260742,
        -5.19116211, -6.03242493, -6.18872833, -5.0980835 , -6.03242493,
        -6.14849091, -5.15044403, -5.58122253, -6.18872833, -5.15044403,
         0.        ])]

Pastebin link to all 142 values. Tried all the solutions from similar SO questions 1 and 2.

The problem is the mp4 video just shows 1 plot shown above and it does not update the values of bar plot in subsequent frames.

All the heights are negative. Are you sure they are just not displayed, because the axes shows positive values? — ImportanceOfBeingErnest, Jan 20 '20 at 02:26

score 0 · Accepted Answer · answered Jan 20 '20 at 23:12

I'm not sure why the method you're using fails to produce the expected output, but clearing and redrawing the plot seems to work correctly:

def barlist(n): 
    return val[n]

fig=plt.figure()
n=100 #Number of frames
x=range(16)
ylim = [-10, 0]
barcollection = plt.bar(x, barlist(0))
plt.ylim(ylim)

def animate(i):
    y = barlist(i+1)
    plt.cla()
    bar = plt.gca().bar(x, barlist(i))
    plt.ylim(ylim)

anim=animation.FuncAnimation(fig,animate, blit=False, repeat=False, frames=4)
anim.save('movie.mp4', writer=animation.FFMpegWriter(fps=1))

Bar-plot animation using matplotlib

1 Answers1