使用matplotlib的时间循环实时绘图?

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我试图用OpenCV实时地从相机中绘制一些数据。然而,实时绘图(使用matplotlib)似乎不起作用。

我已经将这个问题隔离到了这个简单的例子中:

fig=plt.figure()
plt.axis([0,1000,0,1])

i=0
x=list()
y=list()

while i <1000:
    temp_y=np.random.random()
    x.append(i)
    y.append(temp_y)
    plt.scatter(i,temp_y)
    i+=1
    plt.show()

我希望这个例子能分别画出1000点。实际上,窗口会弹出第一个显示的点(可以),然后等待循环完成,然后再填充图形的其余部分。

提问于
用户回答回答于

下面是所讨论的代码的工作版本(至少需要版本Matplotlib 1.1.0,从2011到11-14):

import numpy as np
import matplotlib.pyplot as plt

plt.axis([0, 10, 0, 1])
plt.ion()

for i in range(10):
    y = np.random.random()
    plt.scatter(i, y)
    plt.pause(0.05)

while True:
    plt.pause(0.05)

用户回答回答于

#!/usr/bin/env python

import numpy as np
import time
import matplotlib
matplotlib.use('GTKAgg')
from matplotlib import pyplot as plt


def randomwalk(dims=(256, 256), n=20, sigma=5, alpha=0.95, seed=1):
    """ A simple random walk with memory """

    r, c = dims
    gen = np.random.RandomState(seed)
    pos = gen.rand(2, n) * ((r,), (c,))
    old_delta = gen.randn(2, n) * sigma

    while True:
        delta = (1. - alpha) * gen.randn(2, n) * sigma + alpha * old_delta
        pos += delta
        for ii in xrange(n):
            if not (0. <= pos[0, ii] < r):
                pos[0, ii] = abs(pos[0, ii] % r)
            if not (0. <= pos[1, ii] < c):
                pos[1, ii] = abs(pos[1, ii] % c)
        old_delta = delta
        yield pos


def run(niter=1000, doblit=True):
    """
    Display the simulation using matplotlib, optionally using blit for speed
    """

    fig, ax = plt.subplots(1, 1)
    ax.set_aspect('equal')
    ax.set_xlim(0, 255)
    ax.set_ylim(0, 255)
    ax.hold(True)
    rw = randomwalk()
    x, y = rw.next()

    plt.show(False)
    plt.draw()

    if doblit:
        # cache the background
        background = fig.canvas.copy_from_bbox(ax.bbox)

    points = ax.plot(x, y, 'o')[0]
    tic = time.time()

    for ii in xrange(niter):

        # update the xy data
        x, y = rw.next()
        points.set_data(x, y)

        if doblit:
            # restore background
            fig.canvas.restore_region(background)

            # redraw just the points
            ax.draw_artist(points)

            # fill in the axes rectangle
            fig.canvas.blit(ax.bbox)

        else:
            # redraw everything
            fig.canvas.draw()

    plt.close(fig)
    print "Blit = %s, average FPS: %.2f" % (
        str(doblit), niter / (time.time() - tic))

if __name__ == '__main__':
    run(doblit=False)
    run(doblit=True)

输出:

Blit = False, average FPS: 54.37
Blit = True, average FPS: 438.27

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