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 January 10th, 2017, 09:05 AM #1 Newbie   Joined: Jan 2017 From: London Posts: 4 Thanks: 0 Looking for a formula to work out new values based on changing the Max and Min of... Hi, not sure if this is the best place to ask - please let me know if there's a more suitable forum. I've got an irregular range of values ranging from -infinity to -1 (randomizes every time). I want to be able to set a new value for the max and min values, and adjust everything in the range so that they stay in position relative to each other. For example, let's say I have ten values. The lowest is -40 and the highest is -8. I decided I want to make the highest one 0 and the lowest -10. I need to increase the lowest by 30, but the highest by only 8. I then need to increase the numbers in between each by a unique value so that they are in the same position relatively (but over a much smaller range). Anyone able to offer any assistance? Thanks. Last edited by skipjack; January 10th, 2017 at 02:03 PM.
 January 10th, 2017, 01:55 PM #2 Senior Member     Joined: Feb 2010 Posts: 598 Thanks: 87 A simple linear transformation comes to mind. Make two points from the information and find the equation of the line. In your example, you want $\displaystyle -40$ to map to $\displaystyle -10$ and you want $\displaystyle -8$ to map to $\displaystyle 0$. So make two points $\displaystyle (-40,-10)$ and $\displaystyle (-8,0)$. From these two, make an equation for a line. The slope is $\displaystyle \frac{0--10}{-8--40} = \frac{10}{32} = 0.3125$. So an equation for the line is $\displaystyle y = 0.3125x + 2.5$
 January 10th, 2017, 02:05 PM #3 Global Moderator   Joined: Dec 2006 Posts: 16,770 Thanks: 1231 Do the values have to be integers?
 January 11th, 2017, 01:46 AM #4 Newbie   Joined: Jan 2017 From: London Posts: 4 Thanks: 0 mrtwhs - thanks for the formula! I shall put this into system today and see if it fits what I'm trying to do. skipjack - no it doesn't. in fact I doubt it would work with just integers. Thanks guys
 January 20th, 2017, 03:03 AM #5 Newbie   Joined: Jan 2017 From: London Posts: 4 Thanks: 0 Hi folks, sorry I haven't had a chance to look into this for a while. mrtwhs - your formula works perfectly for the above criteria, but I was wondering if we could take it a step further. Basically, all the values are variable, so the original highest and lowest, and the new values, can all change. So I need to incorporate this into the formula. I've been trying a few things but can't get my head around it. Any chance you can think of a solution? Many thanks!
 January 23rd, 2017, 01:06 AM #6 Senior Member   Joined: Apr 2014 From: UK Posts: 709 Thanks: 271 I think what you want is this: Transform a number?
 January 24th, 2017, 06:50 AM #7 Newbie   Joined: Jan 2017 From: London Posts: 4 Thanks: 0 That's EXACTLY what I'm looking for! thanks weirddave!
 January 24th, 2017, 07:23 AM #8 Senior Member   Joined: Apr 2014 From: UK Posts: 709 Thanks: 271 No problem, the most challenging part was trying to find it, I did it longer ago than I thought....

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