I find it curious that when selecting a Logaritmic scale that negative values cannot be charted on an axis.
Here's my thinking. While logarithmic numbers can't be negative, that isn't the purpose of the scale. The scale is simply to determine the relative distance between marks on an axis. The values themselves are what are charted. So, if I were charting growth rates, for instance, my expectation is that I'll have both positive and negative growth rates. If I wanted to place those rates on a logaritmiticly scaled axis, then the axis should have marks distanced from each other beginning at 0 and extending in both the positive and negative directions. The negative spacing would be the same distances as the positive spacing, only in the negative direction. Then, both the negative and positive growth rates could be plotted, with more spacing for those nearer the 10%'s and less spacing between points for those nearer the 400%. It would take out lots of white space that these outliers introduce, thus presenting a clearer relative picture of those plotted points.
--> Community Manager update [Ciara Brennan]
Feature released in Tableau 2018.2
Tableau 2018.2 Features | Tableau Software (Feature 85890)