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
Python3
# importing Qt widgetsfrom PyQt5.QtWidgets import *# importing systemimport sys# importing numpy as npimport numpy as np# importing pyqtgraph as pgimport pyqtgraph as pgfrom PyQt5.QtGui import *from PyQt5.QtCore import *from collections import namedtupleclass 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("Geeksforneveropen 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 appApp = QApplication(sys.argv)# create the instance of our Windowwindow = Window()# start the appsys.exit(App.exec()) |
Output :
