Daniel Voigt Godoy - Deep Learning with PyTorch Step-by-Step A Beginner’s Guide-leanpub

Affine Transformations
An affine transformation is simply a linear transformation (w T x), such as
rotating, scaling, flipping, or shearing, followed by a translation (b).
If you want to learn more about it, and really understand the role of matrices
in linear transformations, including beautiful visualizations, make sure to
check 3Blue1Brown's channel on YouTube, especially the "Essence of linear
algebra" [80] series. It is amazing! Seriously, don’t miss it!
If you have time to watch the entire series, great, but if you need to keep it to
a minimum, stick with these three:
• Linear transformations and matrices—Chapter 3 [81]
• Matrix multiplication as composition—Chapter 4 [82]
• Nonsquare matrices as transformations between dimensions—Chapter 8
[83]
A Two-Dimensional Model
To visualize these effects, we’ll have to keep everything in a two-dimensional
feature space. Our model looks like the figure below.
Figure B.2 - Model diagram
It has one hidden layer with an activation function (and here we can try any of our
choosing), and an output layer followed by a sigmoid function, typical of a binary
classification. The model above corresponds to the following code:
A Two-Dimensional Model | 333