`stats::glm()`

fits a generalized linear model for numeric outcomes. A
linear combination of the predictors is used to model the numeric outcome
via a link function.

## Details

For this engine, there is a single mode: regression

### Tuning Parameters

This engine has no tuning parameters but you can set the `family`

parameter (and/or `link`

) as an engine argument (see below).

### Translation from parsnip to the original package

```
linear_reg() %>%
set_engine("glm") %>%
translate()
```

```
## Linear Regression Model Specification (regression)
##
## Computational engine: glm
##
## Model fit template:
## stats::glm(formula = missing_arg(), data = missing_arg(), weights = missing_arg(),
## family = stats::gaussian)
```

To use a non-default `family`

and/or `link`

, pass in as an argument to
`set_engine()`

:

```
linear_reg() %>%
set_engine("glm", family = stats::poisson(link = "sqrt")) %>%
translate()
```

```
## Linear Regression Model Specification (regression)
##
## Engine-Specific Arguments:
## family = stats::poisson(link = "sqrt")
##
## Computational engine: glm
##
## Model fit template:
## stats::glm(formula = missing_arg(), data = missing_arg(), weights = missing_arg(),
## family = stats::poisson(link = "sqrt"))
```

### Preprocessing requirements

Factor/categorical predictors need to be converted to numeric values
(e.g., dummy or indicator variables) for this engine. When using the
formula method via `fit()`

, parsnip will
convert factor columns to indicators.

### Case weights

This model can utilize case weights during model fitting. To use them,
see the documentation in case_weights and the examples
on `tidymodels.org`

.

The `fit()`

and `fit_xy()`

arguments have arguments called
`case_weights`

that expect vectors of case weights.

*However*, the documentation in `stats::glm()`

assumes
that is specific type of case weights are being used:“Non-NULL weights
can be used to indicate that different observations have different
dispersions (with the values in weights being inversely proportional to
the dispersions); or equivalently, when the elements of weights are
positive integers `w_i`

, that each response `y_i`

is the mean of `w_i`

unit-weight observations. For a binomial GLM prior weights are used to
give the number of trials when the response is the proportion of
successes: they would rarely be used for a Poisson GLM.”

### Saving fitted model objects

This model object contains data that are not required to make predictions. When saving the model for the purpose of prediction, the size of the saved object might be substantially reduced by using functions from the butcher package.

### Examples

The “Fitting and Predicting with parsnip” article contains
examples
for `linear_reg()`

with the `"glm"`

engine.