What’s Tableau’s default base for the Logarithmic scale?
It’s log10. For example, if you have 1,10,100 and 1,000, then the steps are equal in log10. In other words, the difference between 10 and 100 is the same as between 100 and 1,000 as seen in this visualization:
What are logarithms?
The logarithm is the inverse of the power function. The best way to understand logarithms is through a simple example. If we take to the fourth power (10 x 10 x 10 x 10), the result is 10,000. The logarithm (base 10 – see next point) of 10,000 is the power of 10 that gives 10,000. So the logarithm of 10,000 is 4. In other words, if we multiply 10 by itself four times, we get 10,000.
For more information, a great book is Essential Biostatistics.
What’s the advantage of a Logarithmic scale? Besides the fact that the logarithmic scale is easier to read for humans, the distribution becomes Gaussian.
The beauty of the normal distribution stems from the fact, that we know exactly what proportion of the observation lies within one standard deviation. For example, 68.2% lie within one standard deviation. Franco Arda