René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Update legends in plots subclassed from animation.TimedAnimation","articleBody":"Hi, I want to update the legend with the latest y-value in an animated plot. The graph animation is done as the following official [matplotlib example](https://matplotlib.org/examples/animation/subplots.html),  where the implementation of the animated figures are done by subclassing the animation.TimedAnimation class. To exemplify the issue I've modified the example:\r\n\r\n```\r\nimport numpy as np\r\nimport matplotlib.pyplot as plt\r\nfrom matplotlib.lines import Line2D\r\nimport matplotlib.animation as animation\r\n\r\nclass SubplotAnimation(animation.TimedAnimation):\r\n    def __init__(self):\r\n        fig = plt.figure()\r\n        self.ax1 = fig.add_subplot(1, 2, 1)\r\n        self.ax2 = fig.add_subplot(2, 2, 2)\r\n        self.ax3 = fig.add_subplot(2, 2, 4)\r\n\r\n        self.t = np.linspace(0, 80, 400)\r\n        self.x = np.cos(2 * np.pi * self.t / 10.)\r\n        self.y = np.sin(2 * np.pi * self.t / 10.)\r\n        self.z = 10 * self.t\r\n\r\n        self.ax1.set_xlabel('x')\r\n        self.ax1.set_ylabel('y')\r\n        self.line1 = Line2D([], [], color='black', label='_nolegend_')\r\n        self.line1a = Line2D([], [], color='red', linewidth=2, label='_nolegend_')\r\n        self.line1e = Line2D(\r\n            [], [], color='red', marker='o', markeredgecolor='r', label=\"val = 0\")\r\n        self.ax1.add_line(self.line1)\r\n        self.ax1.add_line(self.line1a)\r\n        self.ax1.add_line(self.line1e)\r\n        self.ax1.set_xlim(-1, 1)\r\n        self.ax1.set_ylim(-2, 2)\r\n        self.ax1.set_aspect('equal', 'datalim')\r\n\r\n        self.ax2.set_xlabel('y')\r\n        self.ax2.set_ylabel('z')\r\n        self.line2 = Line2D([], [], color='black')\r\n        self.line2a = Line2D([], [], color='red', linewidth=2)\r\n        self.line2e = Line2D(\r\n            [], [], color='red', marker='o', markeredgecolor='r')\r\n        self.ax2.add_line(self.line2)\r\n        self.ax2.add_line(self.line2a)\r\n        self.ax2.add_line(self.line2e)\r\n        self.ax2.set_xlim(-1, 1)\r\n        self.ax2.set_ylim(0, 800)\r\n\r\n        self.ax3.set_xlabel('x')\r\n        self.ax3.set_ylabel('z')\r\n        self.line3 = Line2D([], [], color='black')\r\n        self.line3a = Line2D([], [], color='red', linewidth=2)\r\n        self.line3e = Line2D(\r\n            [], [], color='red', marker='o', markeredgecolor='r')\r\n        self.ax3.add_line(self.line3)\r\n        self.ax3.add_line(self.line3a)\r\n        self.ax3.add_line(self.line3e)\r\n        self.ax3.set_xlim(-1, 1)\r\n        self.ax3.set_ylim(0, 800)\r\n\r\n        self.ax1.legend()\r\n        animation.TimedAnimation.__init__(self, fig, interval=50, blit=True)\r\n\r\n    def _draw_frame(self, framedata):\r\n        i = framedata\r\n        head = i - 1\r\n        head_slice = (self.t \u003e self.t[i] - 1.0) \u0026 (self.t \u003c self.t[i])\r\n\r\n        self.line1.set_data(self.x[:i], self.y[:i])\r\n        self.line1a.set_data(self.x[head_slice], self.y[head_slice])\r\n        self.line1e.set_data(self.x[head], self.y[head])\r\n        self.ax1.get_legend().texts[0].set_text(\"val = %s\" % self.y[head])\r\n\r\n        self.line2.set_data(self.y[:i], self.z[:i])\r\n        self.line2a.set_data(self.y[head_slice], self.z[head_slice])\r\n        self.line2e.set_data(self.y[head], self.z[head])\r\n\r\n        self.line3.set_data(self.x[:i], self.z[:i])\r\n        self.line3a.set_data(self.x[head_slice], self.z[head_slice])\r\n        self.line3e.set_data(self.x[head], self.z[head])\r\n\r\n        self._drawn_artists = [self.line1, self.line1a, self.line1e,\r\n                               self.line2, self.line2a, self.line2e,\r\n                               self.line3, self.line3a, self.line3e]\r\n\r\n    def new_frame_seq(self):\r\n        return iter(range(self.t.size))\r\n\r\n    def _init_draw(self):\r\n        lines = [self.line1, self.line1a, self.line1e,\r\n                 self.line2, self.line2a, self.line2e,\r\n                 self.line3, self.line3a, self.line3e]\r\n        for l in lines:\r\n            l.set_data([], [])\r\n\r\nani = SubplotAnimation()\r\n# ani.save('test_sub.mp4')\r\nplt.show()\r\n\r\n```\r\n\r\nThe legeend will not update unless the self._drawn_artists is commented out. But I want to keep using that inherited method otherwise the window/animation is lagging seriously. ","author":{"url":"https://github.com/tkgit123","@type":"Person","name":"tkgit123"},"datePublished":"2019-01-21T13:55:48.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/13252/matplotlib/issues/13252"}