title: 'ImmutableDenseNDimArray' - Can't get equation to plot
body: <p>I'm trying to plot an equation, but I can't seem to do it because of the error mentioned above.</p>
  <p>This is a snippet of the code, should work by itself:</p>
  <pre><code>import numpy as np
  from numpy import linspace
  from sympy import *
  import matplotlib.pyplot as plt
  
  x , t = symbols('x t')
  
  test = simplify(-(0.02631027*sin(3*x)+0.1594*cos(3*x))*exp(-1*x))
  test_f = lambdify([x], test, modules=&quot;sympy&quot;)
  
  # Creating vectors X and Y
  x_num = np.linspace(0, 8, 10)
  
  # Plot size
  fig = plt.figure(figsize = (16, 7))
  
  # Create the plot
  plt.plot(x_num, test_f(x_num))  ← Error at this line!
  
  plt.grid(alpha=.4,linestyle='--')
  plt.legend()
  plt.show()
  </code></pre>
  <p>At the line mentioned above, I get that error.</p>
  <p>What should I do differently?</p>