Plotting with python

aayushlakkad

Hello everyone,
This is my first time here, I am quite new to Qt. I am working on a project where I need to plot data from a csv file in a ChartView object. I have created the ui.qml file in QT design studio.
Following are the codes that I am using:

Screen01.ui.qml file:



/*
This is a UI file (.ui.qml) that is intended to be edited in Qt Design Studio only.
It is supposed to be strictly declarative and only uses a subset of QML. If you edit
this file manually, you might introduce QML code that is not supported by Qt Design Studio.
Check out https://doc.qt.io/qtcreator/creator-quick-ui-forms.html for details on .ui.qml files.
*/
import QtQuick
import QtQuick.Controls
import './imports/Plot_Test'
import QtCharts 2.14

Rectangle {
    id: rectangle
    width: 1296
    height: 730
    color: "#6e9ccc"

    ChartView {
        id: spline_view
        anchors.left: parent.left
        anchors.right: parent.right
        anchors.top: parent.top
        anchors.bottom: parent.bottom
        anchors.bottomMargin: 20
        anchors.topMargin: 20
        anchors.rightMargin: 20
        anchors.leftMargin: 20
        SplineSeries {
            id: serie
            name: "Series"
            axisX: ValuesAxis {
                color: "#1c2b95"
                gridLineColor: "#6e9ccc"
                min: 0
                max: 10
                tickCount: 6
            }

            axisY: ValuesAxis {
                color: "#1c2b95"
                gridLineColor: "#6e9ccc"
                min: 0
                max: 30000
                tickCount: 6
            }

            Component.Component.onCompleted: {
                var series = spline_view.createSeries(ChartView.SeriesTypeSpline,"Random",axisX,axisY)
                helper.serie()
            }
        }
    }
}

data_plot.py file

import pandas as pd
from PySide6.QtCore import QPointF, Qt, QObject
from PySide6.QtCharts import QChart, QChartView, QSplineSeries, QValueAxis, QXYSeries
from PySide6 import QtCore

class Helper(QtCore.QObject):
    serieChanged = QtCore.Signal()

    def __init__(self, parent=None):
        super(Helper, self).__init__(parent)
        self._serie = None

    def serie(self):
        return self._serie

    def setSerie(self, serie):
        if self._serie == serie:
            return
        self._serie = serie
        self.serieChanged.emit()

    serie = QtCore.Property(QSplineSeries, fget=serie, fset=setSerie, notify=serieChanged)

    @QtCore.Slot(list)
    def replace_points(self, points):
        if self._serie is not None:
            self._serie.replace(points)

class Provider(QtCore.QObject):
    pointsChanged = QtCore.Signal(list)

    # def __init__(self, parent=None):
    #     super(Provider, self).__init__(parent)
    #     timer = QtCore.QTimer(
    #         self, 
    #         interval=100,
    #         timeout=self.generate_points
    #     )
    #     timer.start()

    @QtCore.Slot()
    def generate_points(self):
        points = []
        df = pd.read_csv('NK_Heavy.csv')
        x = df['x']
        for i in range(len(x)):
            point = QtCore.QPointF(i, x)
            points.append(point)
        self.pointsChanged.emit(points)

main.py file:

# This Python file uses the following encoding: utf-8
import os
from pathlib import Path
import sys

from PySide6.QtCore import QCoreApplication, Qt, QUrl
from PySide6.QtWidgets import QApplication
from PySide6.QtQml import QQmlApplicationEngine

import data_plot

CURRENT_DIRECTORY = Path(__file__).resolve().parent


def main():
    app = QApplication(sys.argv)
    helper = data_plot.Helper()
    provider = data_plot.Provider()
    provider.pointsChanged.connect(helper.replace_points)
    engine = QQmlApplicationEngine()
    engine.rootContext().setContextProperty('helper', helper)
    filename = os.fspath(CURRENT_DIRECTORY / "main.qml")
    url = QUrl.fromLocalFile(filename)

    def handle_object_created(obj, obj_url):
        if obj is None and url == obj_url:
            QCoreApplication.exit(-1)

    engine.objectCreated.connect(handle_object_created, Qt.QueuedConnection)
    engine.load(url)

    sys.exit(app.exec())


if __name__ == "__main__":
    main()

On running the following code, I am not able to get the plot and it shows the error as:

QMetaProperty::read: Unable to handle unregistered datatype 'QSplineSeries*' for property 'Helper::serie'

SGaist

Hi and welcome to devnet,

As suggested, you should register that type. See here.

aayushlakkad

Thank you @SGaist I was able to remove the error, but still I am not able to see anything on my plot. It gives a blank chart. Can you help me with a link to a sample code, where I can understand how to send my .csv file data from python to QML?

SGaist

I do not see anywhere in your code a line where you're adding series to the plot.

aayushlakkad

That's where I am confused, I tried adding it through qml file. I am following the example mentioned in this link I just removed the timer part, as I don't want an updating plot.
link: https://stackoverflow.com/questions/55257134/how-can-i-change-all-the-points-in-an-xyseries-in-qml-or-pyside2

SGaist

You need to trigger the timer once otherwise no data will be generated.

aayushlakkad

@SGaist Thank you for your response, I was able to plot the data using following changes to my code:

main.qml:

Component.onCompleted:  {
            console.log("This is main.QML")
            var plot = spline_view.createSeries(ChartView.SeriesTypeSpline,"Random",axisX,axisY)
            plotter.fill_serie(plot)
            // console.log(plotter.fill_serie(plot))
            var ymax = plotter.max_yaxis(axisY)
            var ymin = plotter.min_yaxis(axisY)
            var xmax = plotter.max_xaxis(axisX)
            var xmin = plotter.min_xaxis(axisX)            
                }

data_plot.py:

class DataModel(QObject):
    @Slot(QSplineSeries)
    def fill_serie(self, plot):
        self.df = pd.read_csv('gvk_normal_minus_ambient.csv')
        x = self.df['x']
        count = 0
        l = []
        for i in range(0,len(x)):
            point = QPointF(count, x[i])
            # point =  x[i]
            plot.append(point)
            count += 1
        # https://doc.qt.io/qt-5/qml-qtcharts-scatterseries.html#borderColor-prop
        # plot.setProperty("borderColor", QtGui.QColor("salmon"))
        # https://doc.qt.io/qt-5/qml-qtcharts-scatterseries.html#brush-prop
        plot.setProperty("color", QtGui.QBrush(QtGui.QColor("red")))
        # https://doc.qt.io/qt-5/qml-qtcharts-scatterseries.html#borderColor-prop
        plot.setProperty("borderWidth", 4.0)

    @Slot(QValueAxis)
    def min_yaxis(self, yaxis):
        yaxis.setProperty('min', min(self.df['x']))
    
    @Slot(QValueAxis)
    def max_yaxis(self, yaxis):
        yaxis.setProperty('max', max(self.df['x']))

    @Slot(QValueAxis)
    def min_xaxis(self, xaxis):
        xaxis.setProperty('min', 0)
        xaxis.setProperty('tickCount', 6)
        xaxis.setProperty('tickType', 'TicksDynamic')

    @Slot(QValueAxis)
    def max_xaxis(self, xaxis):
        xaxis.setProperty('max', len(self.df['x']))

But the problem is:
The sampling frequency of the data is 10hz. So when I plot all the data, as shown in data_plot.py. I get following graph:

As you can see, the tick values for x-axis are 0-300, but I want to make it from 0-30. I searched all over the internet to set custom labels for x-ticks but I didn't find any solution.

SGaist

This is a different issue that should have it's own thread as it's not related to the problem at hand.

You should also mark this thread as solved.