Assume we have a multiple logistic regression model with 3 continuous independent variables (x1,x2,x3).
I understand that if we want to create an elasticity curve for a continuous variable of interest (let's say x1) in a multiple logistic regression model, first we need to control for all the other continuous variables (x2 and x3) by averaging them and using the averages in the logistic regression equation to generate the predicted probabilities (y^) over a range of expected values for the variable of interest, x1. (see Miller, Marketing Data Science, ch.2 fig 2.4)
My question is what if we have a binary variable and a categorical variable in the model. How do we control for them? I would assume that we have to create a separate curve for each combination of the 2 categorical variables.
Any guidance would be much appreciated.