PyQtGraph – Show Text as Spots on Scatter Plot Graph

In this article, we will see how we can create a scatter plot graph in the PyQtGraph module which shows text instead of symbols as spots. 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 scatter plot (aka scatter chart, scatter graph) uses dots to represent values for two different numeric variables. It is a type of plot or mathematical diagram using Cartesian coordinates to display values for typically two variables for a set of data. The position of each dot on the horizontal and vertical axis indicates values for an individual data point. The main concept of showing text as spots is that we will create a text which will act as the spots.

We can create a plot window and create scatter plot graph on it with the help of commands given below.

# creating a pyqtgraph plot window
plt = pg.plot()

# creating a scatter plot graph of size = 10
scatter = pg.ScatterPlotItem(size=10)

Approach:
1. Import pyqtgraph, pyqt5 and numpy modules 
2. Create Main window class 
3. Create a plot window object 
4. Create a method for creating label which return the text symbol which is named tuple 
5. Create random strings using numpy 
6. Create random position using numpy for plotting the strings 
7. Create a scatter plot item 
8. Create spots using random strings and position and add them to the scatter plot 
9. Add the scatter plot graph to the plot window 
10. Add plot window and extra label widget to the grid layout of main window

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 Scatter Plot Graph with Text")

        # setting minimum width
        label.setMinimumWidth(130)

        # making label do word wrap
        label.setWordWrap(True)

        # setting configuration options
        pg.setConfigOptions(antialias=True)

        # creating a plot window
        plt = pg.plot()

        # text symbols
        TextSymbol = namedtuple("TextSymbol", "label symbol scale")

        # number of text
        n = 150

        # method for creating label
        def createLabel(label, angle):

            # QPainterPath
            symbol = QPainterPath()

            # creating QFont object
            f = QFont()

            # setting font size
            f.setPointSize(10)

            # adding text
            symbol.addText(0, 0, f, label)

            # getting bounding rectangle
            br = symbol.boundingRect()

            # getting scale
            scale = min(1. / br.width(), 1. / br.height())

            # getting transform object
            tr = QTransform()

            # setting scale to transform object
            tr.scale(scale, scale)

            # rotate the transform
            tr.rotate(angle)

            # translating
            tr.translate(-br.x() - br.width() / 2., -br.y() - br.height() / 2.)

            # returning text symbol
            return TextSymbol(label, tr.map(symbol), 0.1 / scale)

        # creating a random string
        def random_str(): return (
            ''.join([chr(np.random.randint(ord('A'), ord('z')))
                     for i in range(np.random.randint(1, 5))]),
            np.random.randint(0, 360))

        # plotting the scatter plot
        scatter = pg.ScatterPlotItem(size=10, pen=pg.mkPen('w'), pxMode=True)

        # getting random position
        pos = np.random.normal(size=(2, n), scale=1e-5)

        # creating spots
        spots = [{'pos': pos[:, i], 'data': 1, 'brush': pg.intColor(i, n), 'symbol': i % 5, 'size': 5 + i / 10.} for i
                 in range(n)]

        # adding spots to the scatter plot
        scatter.addPoints(spots)

        # spots
        spots = [{'pos': pos[:, i], 'data': 1, 'brush': pg.intColor(i, n), 'symbol': label[1],
                  'size': label[2] * (5 + i / 10.)} for (i, label) in
                 [(i, createLabel(*random_str())) for i in range(n)]]

        # adding points to the scatter plot
        scatter.addPoints(spots)

        # adding scatter plot to the plot window
        plt.addItem(scatter)

        # 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)

# create pyqt5 app
App = QApplication(sys.argv)

# create the instance of our Window
window = Window()

# start the app
sys.exit(App.exec())

Output :