Today I learned


  1. If df2 is a DataFrame, df2['A'] returns a Series whereas both df2[['A']] and df2[['A', 'B']] return a DataFrame.


  1. Embeddings are indeed created for categorical variables. For example, in the Excel sheet on collaborative filtering, Jeremy had created embeddings for user-ids and movie-ids both of which were categorical variables.
  2. Let’s say we do a stride 2 in a CNN. While the output height and width will halve, we still double the number of output channels probably because the output channels detect various features of the images and we care more about capturing those features.