
Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion 
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January 10th, 2017, 08:05 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 01:03 PM. 
January 10th, 2017, 12:55 PM  #2 
Senior Member Joined: Feb 2010 Posts: 674 Thanks: 127 
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 $\displaystyle \frac{010}{840} = \frac{10}{32} = 0.3125$. So an equation for the line is $\displaystyle y = 0.3125x + 2.5$ 
January 10th, 2017, 01:05 PM  #3 
Global Moderator Joined: Dec 2006 Posts: 18,965 Thanks: 1606 
Do the values have to be integers?

January 11th, 2017, 12:46 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, 02:03 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, 12:06 AM  #6 
Senior Member Joined: Apr 2014 From: UK Posts: 867 Thanks: 315 
I think what you want is this: Transform a number? 
January 24th, 2017, 05:50 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, 06:23 AM  #8 
Senior Member Joined: Apr 2014 From: UK Posts: 867 Thanks: 315 
No problem, the most challenging part was trying to find it, I did it longer ago than I thought....


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