In this article we will see how we can set cache mode of the error bar 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.). Error bars are graphical representations of the variability of data and used on graphs to indicate the error or uncertainty in a reported measurement. They give a general idea of how precise a measurement is, or conversely, how far from the reported value the true value might be. Position of error bar item is basically the position of the data from origin which is by default 0, 0 although it can be changed any time. Caching is used to speed up rendering by allocating and rendering to an off-screen pixel buffer, which can be reused when the item requires redrawing. For some paint devices, the cache is stored directly in graphics memory, which makes rendering very quick.
We can create a plot window and create error bar graph on it with the help of commands given below
# creating a pyqtgraph plot window plt = pg.plot() # creating a error bar item object error = pg.ErrorBarItem(x=x, y=y, top=top, bottom=bottom, beam=0.5)
In order to do this we use setCacheMode method with the error bar item object
Syntax : error.setCacheMode(n)
Argument : It takes mode value as argument
Return : It returns None
Below is the implementation
# importing Qt widgets from PyQt5.QtWidgets import *
# importing system import sys
# importing numpy as np import numpy as np
# importing pyqtgraph as pg import pyqtgraph as pg
from PyQt5.QtGui import *
from PyQt5.QtCore import *
from collections import namedtuple
class Window(QMainWindow):
def __init__( self ):
super ().__init__()
# setting title
self .setWindowTitle( "PyQtGraph" )
# setting geometry
self .setGeometry( 100 , 100 , 600 , 500 )
# 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()
# creating a label
label = QLabel( "Geeksforgeeks Error Bar plot" )
# setting minimum width
label.setMinimumWidth( 130 )
# making label do word wrap
label.setWordWrap( True )
# setting configuration options
pg.setConfigOptions(antialias = True )
# creating x-axis values
x = np.array([ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ])
# creating y-axis values
y = np.array([ 5 , 4 , 3 , 2 , 5 , 6 , 4 , 8 , 9 , 8 ])
# creating upper bound values
top = np.array([ 2 , 2 , 2 , 2 , 2 , 2 , 2 , 2 , 2 , 2 ])
# creating lower bound values
bottom = np.array([ 2 , 2 , 2 , 2 , 2 , 2 , 2 , 2 , 2 , 2 ])
# creating a plot window
plt = pg.plot()
# creating a error bar item
error = pg.ErrorBarItem(beam = 0.5 )
# setting data to error bar item
error.setData(x = x, y = y, top = top, bottom = bottom)
# adding error bar item to the plot window
plt.addItem(error)
# plotting the data on plot window
plt.plot(x, y, symbol = 'o' , pen = { 'color' : 0.8 , 'width' : 2 })
# 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(plt, 0 , 1 , 3 , 1 )
# setting this widget as central widget of the main window
self .setCentralWidget(widget)
# setting cache mode of error bar item
error.setCacheMode( 1 )
# create pyqt5 app App = QApplication(sys.argv)
# create the instance of our Window window = Window()
# start the app sys.exit(App. exec ())
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Output :