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PyQtGraph – Getting Chache Mode of Error Bar Graph
  • Last Updated : 24 Oct, 2020

In this article we will see how we can get 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. It can be set with the help of setCacheMode method. 

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 cacheMode method with the error bar item object
Syntax : error.cacheMode()
Argument : It takes no argument
Return : It returns mode value 

Below is the implementation 

Python3






# 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 widow
        self.setCentralWidget(widget)
  
        # setting cache mode of error bar item
        error.setCacheMode(1)
  
        # getting cache mode  of the error bar item
        value = error.cacheMode()
  
        # setting text to the label
        label.setText("Cache Mode : " + str(value))
  
# create pyqt5 app
App = QApplication(sys.argv)
  
# create the instance of our Window
window = Window()
  
# start the app
sys.exit(App.exec())

Output : 
 

 

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