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),
The formula generated could be further modified, e.g. adding covariates.
generator_gamFormula_continuousInteraction( response.var, cont1.var, cont2.var, fx = TRUE, k = NULL )
character class, the variable name for response
character class, the name of the first continuous variable
character class, the name of the second continuous variable
TRUE or FALSE, to be used in smooth term s(). Recommend TRUE.
integer, to be used in smooth term including the interaction term. If NULL (no entry), will use default value as in mgcv::s()