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pythonpython-2.7pyqtpyqt4pyqtgraph

Unable to Update Pyqtgraph Plot with New Data Point

I am working on my first pyqtgraph plot which will be added to a Pyqt GUI. When the button addBtn is pressed, a new data point should be added to the pyqtgraph plot.

Problem: Adding the new x and y data as np.array objects using the setData function returns the error:

TypeError: setData(self, int, QVariant): argument 1 has unexpected type 'numpy.ndarray'

How can we fix the problem?

import sys 
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import pyqtgraph as pg
import time
import numpy as np


class Screen(QMainWindow):
    def __init__(self):
        super(Screen, self).__init__()
        self.initUI()

    def initUI(self):
        self.x = np.array([1,2,3,4])
        self.y = np.array([1,4,9,16])
        self.plt = pg.PlotWidget()
        self.plt.plot(self.x, self.y)

        addBtn = QPushButton('Add Datapoint')
        addBtn.clicked.connect(self.addDataToPlot)
        addBtn.show()

        mainLayout = QVBoxLayout()
        mainLayout.addWidget(addBtn)
        mainLayout.addWidget(self.plt)

        self.mainFrame = QWidget()
        self.mainFrame.setLayout(mainLayout)
        self.setCentralWidget(self.mainFrame)

    def addDataToPlot(self):
        data = {
            'x': 5,
            'y': 25
        }
        np.append(self.x, data['x'])
        np.append(self.y, data['y'])
        self.plt.setData(self.x, self.y)


app = QApplication(sys.argv)
window = Screen()
window.show()
sys.exit(app.exec_())

enter image description here

Solution

  • You must update the data in the plot not in the widget, for this we save it as an attribute.

    def initUI(self):
    self.x = np.array([1,2,3,4])
    self.y = np.array([1,4,9,16])
    self.plt = pg.PlotWidget()
    self.plot = self.plt.plot(self.x, self.y)
    [...]

    Also in your case is not being updated, the function append returns an object that concatenates the input data, so you must save it

    def addDataToPlot(self):
    [...]
    self.x = np.append(self.x, data['x'])
    self.y =np.append(self.y, data['y'])
    self.plot.setData(self.x, self.y)