topic Re: Non linear factor constraint in Discussions

Non linear factor constraint

SerialFox537 — Mon, 11 Dec 2023 12:53:08 GMT

I need to make a design where two factors are linked by a constrain that is non linear.
Given factor A [0,5 to 20] and factor B [5 to 125] that need to fulfill equation B<500*A^-1 for the experiment to work.
Only factor combination below the curve are acceptable.

How do I impose such a constrain?
Thank you for any tip.

Re: Non linear factor constraint

MRB3855 — Mon, 11 Dec 2023 13:15:40 GMT

Hi @SerialFox537 : Perhaps this will get you there.

https://community.jmp.com/kvoqx44227/attachments/kvoqx44227/discovery-us-2013-content/24/1/Sauer_McNeill_Kappele.pdf

Re: Non linear factor constraint

Victor_G — Mon, 11 Dec 2023 14:08:09 GMT

Hi @SerialFox537,

Welcome in the Community !

I think this blog post by @Jed_Campbell about factor constraints in DoE should help you integrate your equation in the "Disallowed Combinations Script" (the third option described) :

To generate points below this curve, you can use this disallowed combination script :

B > 500 * A ^ (-1)

Here an example with a Space-Filling design generated with this constraint (only points below this curve) :

Hope this ressource will help you,

Re: Non linear factor constraint

SerialFox537 — Mon, 11 Dec 2023 14:27:34 GMT

Thank you for your reply.
I did try to input the formula in the disallowed combinations script, but when I try to make the design I receive this error:

And all terms are selected.

Re: Non linear factor constraint

Victor_G — Mon, 11 Dec 2023 16:11:42 GMT

Hi @SerialFox537,

Can you be more specific about the platform you use for the design generation, the factors (only A and B ?) and factors type, as well as the assumed model ?

With the Space-Filling example or with a Custom Design, I have no design generation problem with these settings :

Here is the script as an example to regenerate the 12-runs D-Optimal design :

DOE(
	Custom Design,
	{Add Response( Maximize, "Y", ., ., . ),
	Add Factor( Continuous, 0.5, 20, "A", 0 ),
	Add Factor( Continuous, 5, 125, "B", 0 ), Set Random Seed( 360253698 ),
	Number of Starts( 9706 ), Add Term( {1, 0} ), Add Term( {1, 1} ),
	Add Term( {2, 1} ), Add Term( {1, 1}, {2, 1} ), Add Term( {1, 2} ),
	Add Term( {2, 2} ), Set Sample Size( 12 ),
	Disallowed Combinations( B > 500 * A ^ (-1) ), Simulate Responses( 0 ),
	Save X Matrix( 0 ), Make Design, Set Run Order( Randomize ), Make Table}
)

And datatable is attached.

Hope this answer will help you,

Re: Non linear factor constraint

SerialFox537 — Tue, 12 Dec 2023 09:40:04 GMT

I found what the problem was.
The variables were not named A and B, it was just an example.
One of them was a ratio (m/m) and the formula was getting confused with the division operator within the name of the factor.
Once I changed the name it worked as you showed, thank you :)

Re: Non linear factor constraint

Victor_G — Tue, 12 Dec 2023 09:45:17 GMT

Perfect !

If you want to add the units for specific factors, you can add a column property "Units" to this factor, so that unit is displayed in the name (in parentheses) when using this factor but it won't interact with the modeling or with any platform : Properties That Control the Display of Columns

Hope this might help you,