PyQtGraph – Getting X and Y Co-ordinates of Line in Line Graph

23 Jan, 2022
In this article, we will see how we can get X & Y coordinates of the line i.e origin 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. X and Y are the positions of the line corresponding to the respective axis. It can be set with the help of setX and setY methods.
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 x and y methods with the line objectSyntax : line.x() and line.y()Argument : It takes no argumentReturn : 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 * from PyQt5.QtCore import Qt  # 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("GeeksforGeeks 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 X pos to the line1        line1.setX(-2)         # setting Y pos of line 1        line1.setY(5)         # getting X & Y pos of line 1        valuex = line1.x()        valuey = line1.y()         # setting text to the label        label.setText("X & Y pos : " + str(valuex) + ", " + str(valuey))         # 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 : 
 
simmytarika5
anikakapoor
adnanirshad158
Python-gui
Python-PyQtGraph
Python
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