Log transform

Logarithm transformation (or log transform) is a common feature engineering transformation. Log transform helps to flatten highly skewed values. After the log transformation is applied, the data distribution is normalized.

Let's go over another example to again gain some intuition. Remember when you were 10-year-old and looking at 15-year-old boys and girls and thinking "They are so much older than me!" Now think of a 50-year-old person and another that is 55-year-old. In this case, you might think that the age difference is not that much. In both cases, the age difference is 5 years. However, in the first case a 15-year-old is 50 percent older than the 10-year-old, and in the second case the 55-year-old is only 10 percent older than the 50-year-old.

If we apply a log transform to all these data points it normalizes magnitude differences like this.

Applying a log transform also decreases the effect of the outliers, due to the normalization...