QScatterSeries points invisibles when plotted on QCharts

Question

I'm trying to plot a numpy array using QScatterSeries, however only the axis are updated and the points are not displayed. I'm not sure why it is not working.

• projectionwindow.py

from PySide2.QtCore import Qt
from PySide2.QtWidgets import QWidget, QHBoxLayout
from PySide2.QtGui import QColor, QPen
from PySide2.QtCharts import QtCharts


class ProjectionWindow(QWidget):
    """
    TODO
    """
    def __init__(self, parent=None) -> 'None':
        super().__init__()
        self.setWindowTitle('Projection')
        self.resize(800, 800)
        self.chart = QtCharts.QChart()
        self.chart_view = QtCharts.QChartView(self.chart)
        self.layout = QHBoxLayout(self)
        self.layout.addWidget(self.chart_view)
        self.setLayout(self.layout)
        self.show()


    def loadCharts(self, data: 'ndarray') -> 'None':
        points = QtCharts.QScatterSeries()
        points.setMarkerSize(2.0)
        for i in range(data.shape[0]):
            points.append(data[i, 0], data[i, 1])
        self.chart.addSeries(points)
        self.chart.createDefaultAxes()
        self.chart.show()

This is my current result when calling

• main.py

import sys
import numpy as np
from PySide2.QtWidgets import QApplication
from ui.projectionwindow import ProjectionWindow

if __name__ == "__main__":

    app = QApplication(sys.argv)
    data = np.array([[1,2],
                     [3,4]])
    window = ProjectionWindow(app)
    window.loadCharts(data)

    sys.exit(app.exec_())

Resulted obtained:

Answer 1

You have 2 errors:

• The markerSize is very small that makes it indistinguishable to the eye.
• When establishing a series for the first time, the QChart takes the minimum rectangle so that in your case it is in the corners, so the solution is to change the minimum and maximum value of the axes considering an adequate margin.

def loadCharts(self, data: "ndarray") -> "None":
    points = QtCharts.QScatterSeries()
    points.setMarkerSize(20)
    for i in range(data.shape[0]):
        points.append(data[i, 0], data[i, 1])

    self.chart.addSeries(points)
    self.chart.createDefaultAxes()

    m_x, M_x = min(data[:, 0]), max(data[:, 0])
    m_y, M_y = min(data[:, 1]), max(data[:, 1])

    ax = self.chart.axes(Qt.Horizontal, points)[0]
    ax.setMin(m_x - 1)
    ax.setMax(M_x + 1)

    ay = self.chart.axes(Qt.Vertical, points)[0]
    ay.setMin(m_y - 1)
    ay.setMax(M_y + 1)

Output: