how to write this equation for modelfun?

being "bid-ask spread %" , "participation %", "T", "ADV" and "Size" the data I have, and the rest the parameters to fit.

I am trying to use the fitnlm function, but can't write my equation corrently :/

Thanks!

Answer 1

[Elizabeth Reese]

The way you can do this with so many predictor variables and coefficients is to vectorize the equation. Then you just have to be consistent about how you vectorized. For your case, we could do the following:

This means that X would be a big matrix where each column is one of your predictor variables. For there, you have to be careful with multiplication, division, and exponentiation to ensure they are element-wise operations.

For example, to compute this

you need to execute the following in modelfun(b,x):

(x(:,4)./x(:,5)).^b(7)