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PyQtGraph – Line Graph
  • Last Updated : 25 Sep, 2020

In this article we will see how we can create line graph in the PyQtGraph module. 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 second is to provide tools to aid in rapid application development (for example, property trees such as used in Qt Designer).

A line chart or line plot or line graph or curve chart is a type of chart which displays information as a series of data points called ‘markers’ connected by straight line segments. It is a basic type of chart common in many fields. Line graph is created with the help of plot class in PyQtGraph.

In order to plot the bar graph in PyQtGraph we have to do the following
1. Importing the PyQtgraph module
2. Creating a plot window
3. Create or get the plotting data i.e horizontal and two vertical data for two lines
4. Set range to the plot window
5. Plot the line on the plot window and specifying properties of the line

Below is the implementation

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# importing pyqtgraph as pg
import pyqtgraph as pg
  
# importing QtCore and QtGui from the pyqtgraph module
from pyqtgraph.Qt import QtCore, QtGui
  
# importing numpy as np
import numpy as np
  
# define the data
title = "GeeksforGeeks PyQtGraph"
  
# y values to plot by line 1
y = [2, 8, 6, 8, 6, 11, 14, 13, 18, 19]
  
# y values to plot by line 2
y2 = [3, 1, 5, 8, 9, 11, 16, 17, 14, 16]
x = range(0, 10)
  
# create plot window object
plt = pg.plot()
  
# showing x and y grids
plt.showGrid(x = True, y = True)
  
# adding legend
plt.addLegend()
  
# set properties of the label for y axis
plt.setLabel('left', 'Vertical Values', units ='y')
  
# set properties of the label for x axis
plt.setLabel('bottom', 'Horizontal Vlaues', units ='s')
  
# setting horizontal range
plt.setXRange(0, 10)
  
# setting vertical range
plt.setYRange(0, 20)
  
# setting window title to the plot window
plt.setWindowTitle(title)
  
# ploting line in green color
# with dot symbol as x, not a mandatory field
line1 = plt.plot(x, y, pen ='g', symbol ='x', symbolPen ='g',
                          symbolBrush = 0.2, name ='green')
  
# ploting line2 with blue color
# with dot symbol as o 
line2 = plt.plot(x, y2, pen ='b', symbol ='o', symbolPen ='b',
                             symbolBrush = 0.2, name ='blue')
  
# main method
if __name__ == '__main__':
      
    # importing system
    import sys
      
    # Start Qt event loop unless running in interactive mode or using 
    if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
        QtGui.QApplication.instance().exec_()

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