Generate GAM formula with continuous*continuous interaction

This function will generate a formula in the following format: y ~ ti(x) + ti(z) + ti(x,z), where y is response.var, x is cont1.var, and z is cont2.var. The formula generated could be further modified, e.g. adding covariates.

Usage

gen_gamFormula_contIx(response.var, cont1.var, cont2.var, fx = TRUE, k = NULL)

Arguments

response.var

character class, the variable name for response

cont1.var

character class, the name of the first continuous variable

cont2.var

character class, the name of the second continuous variable

fx

TRUE or FALSE, to be used in smooth term s(). Recommend TRUE.

k

integer, to be used in smooth term including the interaction term. If NULL (no entry), will use default value as in mgcv::s()

Value

The formula generated