[QST] in weather example, weird calculation of average.

[lazykyama]

This question is about intermediate_notebooks/examples/weather.ipynb.

At the last of section "5. Using Inner Joins to Filter Weather Observations", total length of stations (like len(atlanta_stations_df)) is used to calculate average precipitation.
However, the numbers of stations are not the same per year. Therefore, the result values are too small in the case that fewer stations only exist.

Why does this notebook use the total number of stations as a denominator?

[taureandyernv]

assigning to @randerzander , who authored it