log-scaling

• Log scaling computes the logarithm of the raw value.
• In theory, the logarithm could be any base; in practice, log scaling usually calculates the natural logarithm (ln).

Log scaling is helpful when the data conforms to a power law distribution. Casually speaking, a power law distribution looks as follows:

• Low values of X have very high values of Y.
• As the values of X increase, the values of Y quickly decrease.
• Consequently, high values of X have very low values of Y.

Movie ratings are a good example of a power law distribution. In the following figure, notice:

• A few movies have lots of user ratings. (Low values of X have high values of Y.)
• Most movies have very few user ratings. (High values of X have low values of Y.)

Log scaling changes the distribution, which helps train a model that will make better predictions.