chart: how much extra att you need to be equal to 1 extra %stat

Close, but no cigar. This would tell you WHEN an increment by one in either stat will result in a similar change in damage range, not how much one of them should change by to match the unit change of the other. Key: Setting the partials (the amount of change of damage per UNIT change in each variable) equal to each other.

[spoiler=maths don't lie][/spoiler]

I believe what we have to do instead is to integrate both sides of the the partial wrt primaryStat from currentDmg to finalDmg to get the change in damage to correspond to the appropriate change in primaryStat.

I set them equal to each other is because we are assuming change in range is equal. So I did deltaR = deltaR -> A*deltaX = B*deltaY -> deltaX = B*deltaY/A -> deltaX = B/A when deltaY=1.

The result from your last pic goes deltaR = A*deltaX -> deltaX = deltaR/A. Substituting deltaR=B*deltaY in gives deltaX=B*deltaY/A -> deltaX=B/A when deltaY = 1, which would give the same result as what I did.

I just treated dX and deltaX as interchangeable because I was lazy. Thanks for showing that they really are interchangeable with that integral down there.

Instead of trying to obtain a change in primary stat, s1, via derivatives, in this case it is cleaner to set the %stat as a separate variable, then obtain the partial derivatives from there on.

Or in this case, since there's little point trying to complicate things via partials (although it is legit), a simple (1 + K + deltaK)*s1 will do, where K is the %stat in decimals, assuming you're only doing a single-variable change.

Maybe someone should just bother to do a spreadsheet that combines all the partial derivatives together to compare two items up for grabs.

Hadriel
[Math never lies... unless you lied to yourself =P]

Yeah I split S1 into s1*(1+K) in order to get the partial with respect to K in like 1 line. Except the variables were names S1 = TotalMain, s1 = Main, and K = MainPot in my thingy.

And for a spreadsheet it would be probably be easier to just compute the ranges for 2 different items directly than using partials. Computing it directly takes 1 computation total, computing it with partials takes 1 computation per variable involved. The partials change every time a variable is changed.
Not a bad way of checking if the maths are correct though.