List the variables involved in a model fitted with a formula

## Usage

```
model_vars(model, ...)
# S3 method for gam
model_vars(model, ...)
# S3 method for default
model_vars(model, ...)
# S3 method for bam
model_vars(model, ...)
# S3 method for gamm
model_vars(model, ...)
# S3 method for gamm4
model_vars(model, ...)
# S3 method for list
model_vars(model, ...)
```

## Arguments

- model
a fitted model object with a

`$pred.formula`

,`$terms`

component or a`"terms"`

attribute- ...
Arguments passed to other methods. Currently ignored.

## Examples

```
load_mgcv()
# simulate some Gaussian data
df <- data_sim("eg1", n = 50, seed = 2)
# fit a GAM with 1 smooth and 1 linear term
m1 <- gam(y ~ s(x2, k = 7) + x1, data = df, method = "REML")
model_vars(m1)
#> [1] "x1" "x2"
# fit a lm with two linear terms
m2 <- lm(y ~ x2 + x1, data = df)
model_vars(m2)
#> [1] "x2" "x1"
```