A PyQt5 demo with embedded matplotlib figure and toolbar and a QSlider to modify the plot data.

demo_PyQt5_QSlider_matplotlib.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import sys
import numpy as np

from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import QWidget, QMainWindow, QVBoxLayout, QSlider, QApplication

import matplotlib
matplotlib.use('QT5Agg')

import matplotlib.pylab as plt
from matplotlib.backends.backend_qt5agg import FigureCanvas 
from matplotlib.backends.backend_qt5agg import NavigationToolbar2QT as NavigationToolbar

class sliderdemo(QMainWindow):
    
    N = 1000
    
    x_data = np.linspace(0,1, N)
    freq = 1.0
    y_data = np.sin(2.0*np.pi*freq*x_data)
    
    fig = None
    ax1 = None
    pltLine = None
    
    def __init__(self, parent = None):
        super(sliderdemo, self).__init__(parent)
        
        layout = QVBoxLayout()
        
        # create plot and put into layout
        self.fig, self.ax1 = plt.subplots()
        self.plotWidget = FigureCanvas(self.fig)
        layout.addWidget(self.plotWidget)
        
        # add toolbar
        self.addToolBar(Qt.BottomToolBarArea, NavigationToolbar(self.plotWidget, self))
        
        self.sl = QSlider(Qt.Horizontal)
        self.sl.setMinimum(1)
        self.sl.setMaximum(30)
        self.sl.setValue(10)
        self.sl.setTickPosition(QSlider.TicksBelow)
        self.sl.setTickInterval(1)
        
        # initial update so that we have some plotted data on startup
        self.valuechange()
        
        # update along with slider movement
        layout.addWidget(self.sl)
        self.sl.valueChanged.connect(self.valuechange)
        
        # central widget for QMainWindow
        centralWidget = QWidget()
        centralWidget.setLayout(layout)
        self.setCentralWidget(centralWidget)
        self.setWindowTitle("PyQt5 QSlider demo")
        
    def valuechange(self):
        # obtain value from slider
        self.freq = self.sl.value()
        
        # recompute data
        self.y_data = np.sin(2.0*np.pi*self.freq*self.x_data)
        
        if self.pltLine is None:
            # initial plot of data
            self.pltLine = self.ax1.plot(self.x_data, self.y_data)
        else:
            # update data in plot and redraw
            self.pltLine[0].set_data(self.x_data, self.y_data)
            self.fig.canvas.draw()
            self.fig.canvas.flush_events()
        
        
if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = sliderdemo()
    ex.show()
    sys.exit(app.exec_())