PyQtGraph – Getting Scale Factor of Line in Line Graph
In this article we will see how we can get the scale factor of the line of 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.) A line chart or line plot or line graph or curve chart is a type of chart that 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. The line graph is created with the help of plot class in PyQtGraph. The scale factor is the factor that is used as the factor by which data of line is multiplied. It can be set with the help of setScale method.
We can create a plot window and create lines on it with the help of commands given below
# creating a pyqtgraph plot window
plt = pg.plot()
# plotting line in green color
# with dot symbol as x, not a mandatory field
line = plt.plot(x, y, pen='g', symbol='x', symbolPen='g',
symbolBrush=0.2, name='green')
In order to do this we use scale method with the line object
Syntax : line.scale()
Argument : It takes no argument
Return : It returns float value
Below is the implementation
Python3
# importing Qt widgetsfrom PyQt5.QtWidgets import *import sys# importing pyqtgraph as pgimport pyqtgraph as pgfrom PyQt5.QtGui import *# Bar Graph classclass BarGraphItem(pg.BarGraphItem): # constructor which inherit original # BarGraphItem def __init__(self, *args, **kwargs): pg.BarGraphItem.__init__(self, *args, **kwargs) # creating a mouse double click event def mouseDoubleClickEvent(self, e): # setting scale self.setScale(0.2)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 new label label = QLabel("zambiatek Line Plot") # making it multiline label.setWordWrap(True) # y values to plot by line 1 y = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] # 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 Values', units='s') # setting horizontal range plt.setXRange(0, 20) # setting vertical range plt.setYRange(0, 20) # plotting 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') # plotting 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') # setting scale of line 1 line1.setScale(2) # getting scale value of line 1 value = line1.scale() # setting text to the label label.setText("Scale : " + str(value)) # label minimum width label.setMinimumWidth(120) # Creating a grid layout layout = QGridLayout() # setting this layout to the widget widget.setLayout(layout) # adding label to 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)# create pyqt5 appApp = QApplication(sys.argv)# create the instance of our Windowwindow = Window()# start the appsys.exit(App.exec()) |
Output :
