如何强制matplotlib更新图表

Question

我正在尝试制作一个小的图形界面（GUI），这个界面里有一个图表，每次读取到新的数据时，图表都会更新。我不想用定时器来运行这个程序，因为数据到达的时间间隔是不一样的。相反，我想用信号的方式来实现：当读取到数据时，数据收集的函数会发出一个信号，然后绘图的函数在完成绘图后也会发出一个信号。

现在的问题是，当我调用canvas.draw()时，画布并没有立即更新。这个程序运行时，数据收集函数（data_collect()）和绘图函数（paint()）交替发送信号，但图形直到我停止程序后才会更新。我该如何让matplotlib在每次调用paint()时都更新图形呢？

下面是一段相对简单的示例代码，虽然不是最优的，但希望能传达我想做的事情的感觉……

N_length = 150;
count = [0];

def sinval(delay):

    k = 0;
    x = [];

    # set up data vector with sinusoidal data in it.
    while k < N_length:  
        x.append(math.sin(2*math.pi*k/N_length));
        k += 1;

    def next():

        time.sleep(delay);
        outstring = "%0.3e" % (x[count[0]]);

        if (count[0] == (N_length-1)):
            count[0] = 0;
        else:
            count[0] += 1;

        return outstring;

    return next;


class DesignerMainWindow(QtGui.QMainWindow, Ui_mplMainWindow):

    def __init__(self, parent = None):
        super(DesignerMainWindow, self).__init__(parent)
        self.setupUi(self)

        QtCore.QObject.connect(self.mplStartButton, QtCore.SIGNAL("clicked()"), self.start_graph);
        QtCore.QObject.connect(self.mplStopButton, QtCore.SIGNAL("clicked()"), self.stop_graph);
        QtCore.QObject.connect(self.mplQuitButton, QtCore.SIGNAL("clicked()"), QtGui.qApp, QtCore.SLOT("quit()"));
        QtCore.QObject.connect(self, QtCore.SIGNAL("data_collect()"), self.data_collect);
        QtCore.QObject.connect(self, QtCore.SIGNAL("paint()"), self.paint);

    def start_graph(self):

        # generates first "empty" plots
        self.user = [];
        self.l_user, = self.mpl.canvas.ax.plot([], self.user, label='sine wave');

        # set up the axes. 
        self.mpl.canvas.ax.set_xlim(0, 300);
        self.mpl.canvas.ax.set_ylim(-1.1, 1.1);
        self.mpl.canvas.draw();

        # start the data collection process.
        self.delay = 0.05;
        self.next = sinval(self.delay);
        self.emit(QtCore.SIGNAL('data_collect()'));


    def data_collect(self):
        outstring = self.next();
        self.user.append(float(outstring.split()[0]));
        self.l_user.set_data(range(len(self.user)), self.user);
        self.emit(QtCore.SIGNAL('paint()'));


    def paint(self):
        self.mpl.canvas.draw();
        self.emit(QtCore.SIGNAL('data_collect()'));

数据可视化事件驱动 matplotlib 数据更新图形界面信号机制实时绘图画布刷新

如何强制matplotlib更新图表

1 个回答

撰写回答