Simbiology error :- Rule is not a valid Matlab expression

When I am writting a rate rule I am getting this above error message. My rule is

LuxI = (1/Tx) ∗ (((tl_luxI ∗ [mRNA_luxI]) ∗ Tx) − ((dLuxI ∗ [LuxI]) ∗ Tx))

I have seen some of the error messages answers of Matlab but nothing worked in my case.Kindly help me with this.

Answer 1

[Walter Roberson]

Your ∗ characters are all char(8727), unicode U+2217 https://www.compart.com/en/unicode/U+2217 "Asterisk Operator" .

They instead need to be char(42), unicode U+002A https://www.compart.com/en/unicode/U+002A "Asterisk"

[Shivam Thakker]

Thank you sir for your reply.

I have tried changing it and I am still getting the same error. This is the updated equation.

LuxI = (1/Tx) * (((tl_luxI * [mRNA_luxI]) * Tx) − ((dLuxI * [LuxI]) * Tx))

[Walter Roberson]

LuxI = (1/Tx) * (((tl_luxI * [mRNA_luxI]) * Tx) − ((dLuxI * [LuxI]) * Tx))

The − is char(8722) U+2212 https://www.compart.com/en/unicode/U+2212 "Minus sign", but needs to be char(45) U+002D "Hyphen-Minus"

So

LuxI = (1/Tx) * (((tl_luxI * [mRNA_luxI]) * Tx) - ((dLuxI * [LuxI]) * Tx))

[Shivam Thakker]

Thank you so much sir. It completely works.

But I have another issue that when I set the unit of one of species as 1/minute, it is not allowing and getting a message that this is not a valid unit. So I went to Libraries -> Custom Libraries -> Units. There I tried adding this unit but didn't worked. Can you help me with this like how can I set the unit to 1/minute.

[Florian Augustin]

Hi,

the units of species must be specified in amount, amount/length, amount/area, or amount/volume. This is because species in SimBiology represent quantities or concentrations. If necessary (and possible) in your use case, I suggest to use "parameters" instead of "species". This allows you to specify units more freely.

-Florian

[Walter Roberson]

Thanks, Florian, that sounds useful to know.

[Shivam Thakker]

Thank you @Florian Augustin. It worked completely and now I am able to assign the units that I want. Thank you@Walter Roberson and @Florian Augustin for replying and helping me.

[Shivam Thakker]

Actually, sir, I want some help regarding the same. Sir, I am referring to a paper in which they have build a model in Simbiology but they have not given the concentrations and units for all the parameters. So for now I have set the units by myself. So I am getting an error that the "Quantities of different dimensions cannot be added or subtracted". I know that this error is due to the random units(dimensions) that I have set. But can you help me or guide me on how can I remove this kind of error. I have tried unit conversion to true but is not working. Probably I have misunderstood the meaning of unit conversion.

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/4706-unit-conversion-in-simbiology

Unit conversion is for converting between compatible units, such as mm and m, or Newton-metres and Joules.

It does not assign "whatever units that make the calculations work out".