# Generate GAM formula with continuous*continuous interaction

`generator_gamFormula_continuousInteraction.Rd`

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

```
generator_gamFormula_continuousInteraction(
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()