[NB-3] Empty figure and S not defined

[Or Ricon]

Hi,

I noticed on Notebook 3 under SVD - Rank 1 Approximation the following:

1. Line plt.imshow(np.reshape(M[:,140] - low_rank[:,140], dims)[50:150,100:270], cmap='gray'); will output an empty figure (likely because the dimensions are set for the full resolution images.

2. Line plt.imshow(np.reshape(S[:,140], dims)[50:150,100:270], cmap='gray') will fail because S is undefined (likely it should be M). If using M it will also output an empty figure, probably for the same reason above.