Plotting Data with Timestamps using PyQtGraph

In this article, we will see how we can plot data with timestamps using the PyQtGraph module in Python. PyQtGraph is a graphics and user interface library for Python that provides functionality commonly required in designing and science applications. Its primary goals are to provide fast, interactive graphics for displaying data (plots, video, etc.) and the second is to provide tools to aid in rapid application development (for example, property trees such as used in Qt Designer).

In order to install the PyQtGraph we use the command given below.

pip install pyqtgraph

A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. In this tutorial we will see how we can plot timestamps on x-axis and y-axis will have corresponding data with it.

In order to do so we have to do the following 

1. Import the required libraries like pyqtgraph, pyqt5, time and numpy
2. Create a main window class using pyqt5
3. Create a graph window having axisitem set as DateAxisItem for timestamps
4. Now create a data to plot in this example we will plot the sin(1/x^2) with timestamps in the last 100 years
5. With this data plot the line graph
6. Add the graph and other widgets to the layout of central widget of main window.

Below is the implementation.

Python3

# importing Qt widgets
from PyQt5.QtWidgets import *

# importing system
import sys

# time module
import time
from datetime import datetime, timedelta

# importing numpy as np
import numpy as np

# importing pyqtgraph as pg
import pyqtgraph as pg
from PyQt5.QtGui import *
from PyQt5.QtCore import *


class Window(QMainWindow):

    def __init__(self):
        super().__init__()

        # setting title
        self.setWindowTitle("PyQtGraph")

        # setting geometry
        self.setGeometry(100, 100, 900, 550)

        # icon
        icon = QIcon("skin.png")

        # setting icon to the window
        self.setWindowIcon(icon)

        # calling method
        self.UiComponents()

        # showing all the widgets
        self.show()

    # method for components
    def UiComponents(self):

        # creating a widget object
        widget = QWidget()

        # text
        text = "Timestamps Plot"

        # creating a label
        label = QLabel(text)

        # setting minimum width
        label.setMinimumWidth(130)

        # making label do word wrap
        label.setWordWrap(True)

        # Create a plot with a date-time axis (timestamps on x-axis)
        w = pg.PlotWidget(axisItems={'bottom': pg.DateAxisItem()})

        # show the grids  on the graph
        w.showGrid(x=True, y=True)

        # Plotting sin(1/x^2) with timestamps in the last 100 years
        now = time.time()

        # x data
        x = np.linspace(2 * np.pi, 1000 * 2 * np.pi, 8301)

        # plot the data
        w.plot(now - (2 * np.pi / x) ** 2 * 100 *
               np.pi * 1e7, np.sin(x), symbol='o')

        # Creating a grid layout
        layout = QGridLayout()

        # minimum width value of the label
        label.setMinimumWidth(130)

        # setting this layout to the widget
        widget.setLayout(layout)

        # adding label in the layout
        layout.addWidget(label, 1, 0)

        # plot window goes on right side, spanning 3 rows
        layout.addWidget(w, 0, 1, 3, 1)

        # setting this widget as central widget of the main window
        self.setCentralWidget(widget)


# create pyqt5 app
App = QApplication(sys.argv)

# create the instance of our Window
window = Window()

# start the app
sys.exit(App.exec())

Output :