PyQtGraph – Getting Opacity Property of Error Bar Graph
In this article, we will see how we can get the opacity property of the error bar graph in the PyQtGraph module. The 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. Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc. It can be set with the help of the setOpacity() 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 opacity() method with the error bar item object:
Syntax : error.opacity()
Argument : It takes no argument
Return : It returns float value
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("Geeksforzambiatek 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 opacity of error bar item error.setOpacity(0.3) # getting opacity of the error bar item value = error.opacity() # setting text to the label label.setText("Opacity : " + str(value))# create pyqt5 appApp = QApplication(sys.argv)# create the instance of our Windowwindow = Window()# start the appsys.exit(App.exec()) |
Output:
