Re: Formulize - Sum of the Variables divided by the Number of Variables

[Alison Reynolds]

Hi Nevi,

First let me clarify exactly what you are looking for.  Is the idea that given variable x1, x2, ... x8, you want the model produced to look like:

z = (x1 + x2) / 2

or

z = (x1 + x2 + x3) / 3

where the variables could be any subset of the 8 variables, and the denominator will be the number of variables?  I.e. you expect that z will be the mean of some subset of the input variables?

If my understanding is correct, then I think you can use a target expression that looks like this:

y = (step(f0())*x1 + step(f1())*x2 + step(f2())*x3)/(step(f0()) + step(f1()) + step(f2()))

(Mine is set up for 3 input variables; you'll need to update it for 8).  The expressions step(fn()) will map to either 0 or 1.  On the numerator that will either include or exclude a variable from being included in the sum of variables.  On the denominator it will contribute to the count of variables.  I've attached a sample project that shows that expression used in 2 searches.  The solutions produced (once Eureqa has simplified them) are:

y = 0.5*x1 + 0.5*x2

and 

y = 0.3333*x1 + 0.3333*x2 + 0.3333*x3

Those of course can be rewritten in the format you are looking for..

y = (x1 + x2) / 2

and

y = (x1 + x2 + x3) / 3

Let me know if that's what you were looking for.

Alison

On Mon, Jul 22, 2013 at 12:59 AM, aidabet <aid...@cox.net> wrote:

Another question

Example Target Expression

z = f(x1, x2, x3, x4, x5, x6, x7, x8)

 

I’m looking for a way to Sum the number of variables being considered for a Solution and divide the Sum of the Variables by the Number of Variables, all included in the Final Solution.

 

So the Final Solution would resemble

z = f(( x1 + x2 ) / 2 )  if two variables used

z = f(( x1 + x2 + x3 ) / 3 ) if three variables used

 

If it’s possible your help is appreciated

Thanks

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