Prerequisites: Insertion Sort, Introduction to Matplotlib
Visualizing algorithms makes it easier to understand them by analyzing and comparing the number of operations that took place to compare and swap the elements. 3D visualization of algorithms is less common, for this we will use matplotlib to plot bar graphs and animate them to represent the elements of the array.
Approach:
- We will generate an array with random elements.
- The algorithm will be called on that array and yield statement will be used instead of return statement for visualization purposes.
- We will yield the current states of the array after comparing and swapping. Hence the algorithm will return a generator object.
- Matplotlib animation will be used to visualize the comparing and swapping of the array.
- We will then plot the graph, which will return an object of Poly3dCollection using which further animation will be done.
Below is the implementation.
Python3
# import the modules import matplotlib.pyplot as plt from matplotlib.animation import FuncAnimation from mpl_toolkits.mplot3d import axes3d import matplotlib as mp import numpy as np import random # Array size n = 11 # insertion sort algorithm def insertionsort(a): for j in range(1, len(a)): key = a[j] i = j-1 while(i >= 0 and a[i] > key): a[i+1] = a[i] i -= 1 yield a a[i+1] = key yield a # method to plot graph def showGraph(n): # for random unique values a = [i for i in range(1, n+1)] random.shuffle(a) datasetName = 'Random' algoName = 'Insertion Sort' # generator object returned by the function generator = insertionsort(a) # the style of the graph plt.style.use('fivethirtyeight') # set bar colors data_normalizer = mp.colors.Normalize() color_map = mp.colors.LinearSegmentedColormap( "my_map", { "red": [(0, 1.0, 1.0), (1.0, .5, .5)], "green": [(0, 0.5, 0.5), (1.0, 0, 0)], "blue": [(0, 0.50, 0.5), (1.0, 0, 0)] } ) # plot the array fig = plt.figure() ax = fig.add_subplot(projection='3d') # the z values and position of the bars z = np.zeros(n) dx = np.ones(n) dy = np.ones(n) dz = [i for i in range(len(a))] # plot 3d bars rects = ax.bar3d(range(len(a)), a, z, dx, dy, dz, color=color_map(data_normalizer(range(n)))) ax.set_xlim(0, len(a)) ax.set_ylim(0, int(1.1*len(a))) ax.set_title("ALGORITHM : "+algoName+"\n"+"DATA SET : "+datasetName, fontdict={'fontsize': 13, 'fontweight': 'medium', 'color': '#E4365D'}) # 2D text placed on the upper left # based on the axes fraction text = ax.text2D(0.1, 0.95, "", horizontalalignment='center', verticalalignment='center', transform=ax.transAxes, color="#E4365D") iteration = [0] # function for animating def animate(A, rects, iteration): # to clear the bars from the # Poly3DCollection object ax.collections.clear() ax.bar3d(range(len(a)), A, z, dx, dy, dz, color=color_map(data_normalizer(range(n)))) iteration[0] += 1 text.set_text("iterations : {}".format(iteration[0])) anim = FuncAnimation(fig, func=animate, fargs=(rects, iteration), frames=generator, interval=50, repeat=False) plt.show() # Driver Code showGraph(n) |
Output :
