04-20-2021, 01:09 AM | #1 |
Join Date: May 2012
Location: New Hampshire, USA
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speed range table equation
can anyone tell me what the actual equation is for the speed/range table? I'm trying to create a spreadsheet that will auto-calculate the modifier for a given value. I know it involves logarithms but don't really know how to use them that well. I'm working in google docs.
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04-20-2021, 01:23 AM | #2 |
Join Date: Mar 2016
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Re: speed range table equation
You're not going to get a broadly usable equation because it rounds differently at different points.
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04-20-2021, 02:35 AM | #3 |
Join Date: Jul 2008
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Re: speed range table equation
Fundamentally, the SSR modifier is equal to six times the log of the measure divided by the zero point.
For distance, that's 6 * log(d / 2yd) Use base 10 logs. The positions in the tables are shifted to put the breakpoints at 'nice' numbers though If you're committed to using the table as written rather than having the formula replace it, well...it could probably be done but it would involve some weird functions to force it to emulate the way the table is rounded.
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04-20-2021, 06:06 AM | #4 |
Join Date: Aug 2004
Location: United Kingdom of Great Britain and some other bits.
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Re: speed range table equation
It isn't elegant, but here a google docs sheet which should do the job.
https://docs.google.com/spreadsheets...it?usp=sharing
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04-20-2021, 06:29 AM | #5 |
Join Date: Jun 2013
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Re: speed range table equation
If you want to keep the current breakpoints, just treating it as linear between them works out just fine - in no small part because the current breakpoints largely are linear, it's just that the slopes keep increasing. What I mean by that is that from -2 to 0 (1, 1.5, 2) and +1 to +3 (3, 5, 7), it's linear (+0.5 per +1 and +2 per +1, respectively), and as there are only 6 unique values (everything else just repeats the same sequence with the decimal point shifted), this means there are only a few cases where you can't draw a straight line through 3 consecutive points (basically 0 to +1 and +3 to +4 are the odd ones out). So, SM +3.7 corresponds to 9.1 yards (7/10ths of the way between 7 and 10).
I'm not certain of an elegant way to have a spreadsheet do that for you, however.
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04-20-2021, 07:12 AM | #6 |
Join Date: Apr 2018
Location: Trondheim, Norway
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Re: speed range table equation
You can check out my Excel Character Sheet (link in signature) for a formula. In the current version (20.3), it's located on the Current Status sheet in cell BR18 (under header "Penalty"). The formula isn't pretty, and could probably be simplified, at least a little, but it does the trick. It includes "to hit" penalty for the size of the target at the end of the formula, but you can easily remove that part, if you don't want it.
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04-20-2021, 07:49 AM | #7 |
Hero of Democracy
Join Date: Mar 2012
Location: far from the ocean
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Re: speed range table equation
So if you don't mind the slightly off rounding, there is always the equation:
Code:
=Round(Log(D7,10)*6-2,0) replace D7 with what you need. the rounding really isn't that bad, its just not exact. for most purposes, this will give you what you need.
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04-20-2021, 09:52 AM | #8 |
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Join Date: Sep 2004
Location: Southeast NC
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Re: speed range table equation
If you needed a spreadsheet formula, you could duplicate the SSR table to infinity in both directions with a simple lookup.
=vlookup('size'/int(log('size',10)),'table',2)+6*int(log('size',10 )) Where 'size' points to the size in yards and 'table' points to a table of SM from -2 (1 yard) to 3 (7 yards). That treats SM+1 as staring just beyond 2 yards, rather than rounding to the closest SM, which GURPS is sometimes inconsistent about (21 yards is -7 for range, but 2.1 yards is a tallish SM+0 human). It also doesn't account for the small differences introduced by the canon chart switching to inches at the small end. Edit to add: if you want to get really fancy, you could add a drop down selector to pick inches (an additional -11 to SM), feet (-3), or miles (+17 or +18 depending on how you want to round).
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04-20-2021, 10:00 AM | #9 |
Join Date: Jul 2008
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Re: speed range table equation
This is the only place it's inconsistent that way, and seems to be a consequence of the principle that 'a human character's build only has mechanical effects if you want it to'.
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04-20-2021, 10:55 AM | #10 |
Join Date: Jun 2005
Location: Lawrence, KS
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Re: speed range table equation
I don't think there's a neat way to do this with a spreadsheet, but if you want a fractional modifier, for a number that falls between L and U, you can take
(log X - log L)/(log U - log L) or log (X/L)/log (U/L) and add it to the modifier for L. So, for example, if X is 2.5, that falls between 2 and 3, so log (2.5/2)/log (3/2) = log 1.25/log 1.5 = 0.10/0.18 = 0.55 and adding that to 0 (the modifier for 2) is 0.55.
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