I'm new to R and need help getting a rcspline.plot to work. I have a dataset (Fish_lesion) with the presence/absence of a parasite (coccidia) and a variety of fish measurements (total length, weight, age).
I am using logistic regression to determine if there is a relationship between coccidia infection and age or size of fish. I would like to determine if there is a linear relationship between the log odds and the predictor variables. I was given the following to generate an rcspline.plot: