Questions and discussion for this lecture live here. Fire away by hitting Reply below 
Greetings,
I used the same code of your program and run it. I got this message at the last stage of plot:
#Plotting
fig, axes = plt.subplots(figsize=(15,8),nrows=1,ncols=3)
modeCoords1 = np.array([0, eVecA1[0], eVecA1[1], eVecA1[2]], float)
axes[0].plot([0,0,0,0],[0, h1, h1+h2, h1+h2+h3],‘-k’)
axes[0].plot(modeCoords1,[0, h1, h1+h2, h1+h2+h3],‘-’)
axes[0].plot(modeCoords1[1],[h1],‘-o’,markerfacecolor=‘red’, markeredgecolor=‘k’, markersize=13)
axes[0].plot(modeCoords1[2],[h1+h2],‘-o’,markerfacecolor=‘red’, markeredgecolor=‘k’, markersize=13)
axes[0].plot(modeCoords1[3],[h1+h2+h3],‘-o’,markerfacecolor=‘red’, markeredgecolor=‘k’, markersize=13)
axes[0].set_xlabel(‘Relative amplitude’)
axes[0].set_ylabel(‘Height (m)’)
axes[0].set_title(‘Mode shape for $\omega_1$ = {one} rads/sec’.format(one=round(OmegaA,1)))
axes[0].set_xlim([-2.5, 2.5])
axes[0].grid()
The error was:
ValueError Traceback (most recent call last)
Cell In[41], line 4
1 #Plotting
2 fig, axes = plt.subplots(figsize=(15,8),nrows=1,ncols=3)
----> 4 modeCoords1 = np.array([0, eVecA1[0], eVecA1[1], eVecA1[2]], float)
5 axes[0].plot([0,0,0,0],[0, h1, h1+h2, h1+h2+h3],‘-k’)
6 axes[0].plot(modeCoords1,[0, h1, h1+h2, h1+h2+h3],‘-’)
ValueError: setting an array element with a sequence. The requested array has an inhomogeneous shape after 1 dimensions. The detected shape was (4,) + inhomogeneous part.
Please let me know what is the issue:
Hey @joejavady, the issues arises because eVecA1[0], eVecA1[1], and eVecA1[2] all actually evaluate to a numpy array, we see this if we evaluate,
print(type(eVecA1[0]))
…we get <class 'numpy.ndarray'>. At the original time of writing, this was acceptible syntax - but not any longer. So, we need to specify or index into the value inside the array, as follows:
eVecA1[0][0]
…which will yield 1.0 rather than [1.0].
So you would alter line four as follows:
modeCoords1 = np.array([0, eVecA1[0][0], eVecA1[1][0], eVecA1[2][0]], float)
Make sure to do the same for lines 16 and 28. This will resolve the issue.
(Note that the code and notebook for this lecture have been updated to reflect the correction outlined above.)
ok, thank you. it woks now
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Hi Sean @Sean ,
Either it is a typo or i am missing something : In the below screen shot this omega in sine shall be omega_n right ? I was expecting that omega to be omega_n considering our matrix notation is for ‘‘Undamped Free Vibration Equation’’. Typo or maybe because it is trivial , it is okay to not write in that way maybe, i am just trying to get the correct terminology and notation for my reference.
Thanks a lot,
Cheers
Burak
No typo.
At this stage in the solution omega simply represents a parameter variable. It’s specific values, w_n where n=1,2, emerge when we solve the characteristic equation.
S
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