How to define unequal intervals for x-axis corresponding to the x-axis from a picture

I expect that the answer to this is probably going to come from your knowledge of the math around the problem rather than our knowledge of Excel.

Looking up Froude number (and Eotvos number) on Wikipedia, it appears that these are quantities from fluid dynamics http://en.wikipedia.org/wiki/Froude_number Just looking at the different definitions of Froude number, there are a lot of expressions that employ the square root function (and nothing that references the logarithmic function. Is it possible that this kind of chart is using a square root axis? Jon Peltier (peltiertech.com) has several tutorials for what he calls the "arbitrary axis" technique, one that shows how to build a reciprocal (1/x) axis. The same kind of technique could easily be used for a square root axis (or whatever the x axis "function" turns out to be).

I haven't been able to access Jon's site for a while, either.

The technique is basically the same one Tushar Mehta uses in his "flexible log scale" tutorial for older versions of Excel: http://tushar-mehta.com/excel/newsgr...cale/help.html You will need to calculate sqrt(x) in a column which will be used for the x values in your chart. Then, you create a dummy series which you will plot and label to be the axis you want displayed.