python - why am I getting this error shape mismatch: two or more arrays have incompatible dimensions on axis 0 -

i've hat wave given initial conditions. x , y between 0.5 , 1, u = 2, otherwise u = 1. x , y vary 0 2.

the wave time dependent plotting pausing clearing 3d graph.

here code:

# import modules required  import numpy np import matplotlib.pyplot plt import pylab py mpl_toolkits.mplot3d import axes3d  #define grid  x = np.linspace(0,2,21) y = np.linspace(0,2,21) u = np.ones((21,21)) c = 1 dt = 0.01 dx = 0.1 dy = 0.1   #initial conditions  in range (21):     if (0.5<=x[i]<=1):         j in range (21):             if (0.5<=y[j]<=1):                 u[i,j] = 2  #prop , plot  = np.ones((21,21))  f in range (100):     in range (21):         j in range (21):             up[i,j] = u[i,j] - ((c*dt)/(dx))*(u[i,j] - u[i-1,j]) - ((c*dt)/(dy))*(u[i,j] - u[i,j-1])                  u =     fig = plt.figure(figsize=(11,7), dpi=100)     ax = fig.gca(projection='3d')     x,y = np.meshgrid(x,y)     surf = ax.plot_wireframe(x,y,u[:])     plt.show() 

you getting error because ax.plot_wireframe uses np.broadcast_arrays expects input arrays have same shape. what's happening each iteration of for f in range (100): line x,y = np.meshgrid(x,y) changing shape of x , y. paste these lines code , see yourself.

print x.shape, y.shape x,y = np.meshgrid(x,y) print x.shape, y.shape 

try moving x,y = np.meshgrid(x,y) out of loop.

#prop , plot  = np.ones((21,21)) x,y = np.meshgrid(x,y)  f in range (100):     in range (21):         j in range (21):             up[i,j] = u[i,j] - ((c*dt)/(dx))*(u[i,j] - u[i-1,j]) - ((c*dt)/(dy))*(u[i,j] - u[i,j-1])                  u =     fig = plt.figure(figsize=(11,7), dpi=100)     ax = fig.gca(projection='3d')     surf = ax.plot_wireframe(x,y,u[:])     plt.show()