title: Plotting Only One Point in 3D Matplotlib
body: <p>I'm trying to plot the solution of a linear system with 3 planes, the solution is the point (1,1,1) I've plotted the point with point command but I suspect the point is not in the right place:</p>
  
  <pre><code>ax.plot([1.], [1.], [1.], markerfacecolor='k', markeredgecolor='k', marker='o', markersize=5, alpha=0.6)
  </code></pre>
  
  <p>Thanks
  Ok, the code is:</p>
  
  <pre><code>#/usr/bin/env python3
  # -*- coding: utf-8 -*-
  
  
  import numpy as np
  import matplotlib.pyplot as plt
  from mpl_toolkits.mplot3d import Axes3D
  from sympy.solvers import *
  from sympy import *
  from matplotlib import rcParams
  
  
  # Activating LateX
  rcParams['text.latex.unicode'] = True
  rcParams['text.usetex'] = True
  rcParams['text.latex.preamble'] = '\\usepackage{amsthm}', '\\usepackage{amsmath}', '\\usepackage{amssymb}',
  '\\usepackage{amsfonts}', '\\usepackage[T1]{fontenc}', '\\usepackage[utf8]{inputenc}'
  
  
  # Declaring the three planes as functions
  f1 = lambda x, y: x + y -1
  f2 = lambda x, y: 1 - x + y
  f3 = lambda x, y: 1 + x - y
  
  # Declaring symbolic variables
  x = Symbol('x')
  y = Symbol('y')
  z = Symbol('z')
  
  # Solving the linear system
  fun1 = x+y-z-1
  fun2 = x-y+z-1
  fun3 = -x+y+z-1
  solucion = solve([fun1, fun2, fun3], [x, y, z])
  
  # Printing the solution
  pprint(('Solución Del Sistema es: {}').format(solucion))
  
  
  # Stablishing our ranges for our variables
  x1 = y1 = np.arange(-5, 5, 0.25)
  ceros = np.zeros(len(x1))
  
  # Stablishing our meshgrid
  x, y = np.meshgrid(x1, y1)
  
  # Our 3D Canvas Figure Plot
  fig = plt.figure()
  ax = fig.add_subplot(111, projection='3d')
  
  # Plotting the 3 planes
  ax.plot_surface(x, y, f1(x, y), rstride=1, cstride=1, linewidth=0, antialiased=True, color='blue')
  ax.plot_surface(x, y, f2(x, y), rstride=1, cstride=1, linewidth=0, antialiased=True, color='red')
  ax.plot_surface(x, y, f3(x, y), rstride=1, cstride=1, linewidth=0, antialiased=True, color='green')
  ax.plot([1.], [1.], [1.], markerfacecolor='k', markeredgecolor='k', marker='o', markersize=5, alpha=0.6)
  
  # Putting the limits in the axes
  ax.set_xlim(-10, 10)
  ax.set_ylim(-10, 10)
  ax.set_zlim(-10, 10)
  
  # Writing the axis labels
  ax.set_xlabel('x', color='blue')
  ax.set_ylabel('y', color='blue')
  ax.set_zlabel('z', color='blue')
  
  # Writing The Title of The Plot
  ax.set_title(r'$Graphical\; Resolution\; Linear\; System\; 3 \times 3$', fontsize=18)
  
  # Stablishing the plots of our legend labels
  blue_proxy = plt.Rectangle((0, 0), 1, 1, fc='b')
  red_proxy = plt.Rectangle((0, 0), 1, 1, fc='r')
  green_proxy = plt.Rectangle((0, 0), 1, 1, fc='g')
  black_proxy = plt.Line2D([0], [0], linestyle="none", marker='o', alpha=0.6, markersize=10, markerfacecolor='black')
  
  # Drawing Our Legend
  ax.legend([blue_proxy,red_proxy, green_proxy, black_proxy], [r'$x+y-z=1$',r'$x-y+z=1$', r'$-x+y+z=1$', r'$Sol.\; (1,1,1)$'], numpoints=1, loc='upper left')
  
  plt.show()
  </code></pre>
  
  <p>An image:</p>
  
  <p>The z-coordinate of the point (1,1,1) is not at the height 1, it is below 0. So, the point is not drawn in the correct place.
  <img src="https://i.stack.imgur.com/vShf0.png" alt="Image of the code"></p>