topic Re: Customised Mixture Design - how can I set two ingredients to be a constant ratio? in Discussions

Customised Mixture Design - how can I set two ingredients to be a constant ratio?

TDF — Thu, 08 Jun 2023 21:07:20 GMT

My ingredients sum to 88% which I have set in options.

I have set a linear constraint for two ingredients to have a minimum amount greater than the sum of their respective minimum levels.

I have two other variables for which the ratio in each recipe of the two must be a constant. I have tried all the different design options but I cannot find a way to do this, is it possible?

I am using JMP Pro16.

Re: Customised Mixture Design - how can I set two ingredients to be a constant ratio?

Dan_Obermiller — Mon, 13 Dec 2021 14:04:34 GMT

Let's call the factors A and B. If A/B = 0.5, as an example, then that means that A = 0.5B. That also implies that A-0.5B = 0. Specifying two linear constraints should work. A - 0.5 B <=0 and A - 0.5 B >= 0.

Re: Customised Mixture Design - how can I set two ingredients to be a constant ratio?

TDF — Wed, 15 Dec 2021 11:20:38 GMT

Hello Dan

Thanks for the prompt reply, I hadn't thought about entering negative values of an ingredient into the constraint.

However, when I do as you suggested I get the following constraint error (see attached).

Re: Customised Mixture Design - how can I set two ingredients to be a constant ratio?

TDF — Wed, 15 Dec 2021 12:34:42 GMT

However, I have explored the idea further and if I set the second constraint to -0·4999 instead of -0·5 then it works.

Thanks Dan.