# details_poisson_reg_glmnet: Poisson regression via glmnet In parsnip: A Common API to Modeling and Analysis Functions

 details_poisson_reg_glmnet R Documentation

## Poisson regression via glmnet

### Description

`glmnet::glmnet()` uses penalized maximum likelihood to fit a model for count data.

### Details

For this engine, there is a single mode: regression

#### Tuning Parameters

This model has 2 tuning parameters:

• `penalty`: Amount of Regularization (type: double, default: see below)

• `mixture`: Proportion of Lasso Penalty (type: double, default: 1.0)

The `penalty` parameter has no default and requires a single numeric value. For more details about this, and the `glmnet` model in general, see glmnet-details. As for `mixture`:

• `mixture = 1` specifies a pure lasso model,

• `mixture = 0` specifies a ridge regression model, and

• `⁠0 < mixture < 1⁠` specifies an elastic net model, interpolating lasso and ridge.

#### Translation from parsnip to the original package

The poissonreg extension package is required to fit this model.

```library(poissonreg)

poisson_reg(penalty = double(1), mixture = double(1)) %>%
set_engine("glmnet") %>%
translate()
```
```## Poisson Regression Model Specification (regression)
##
## Main Arguments:
##   penalty = 0
##   mixture = double(1)
##
## Computational engine: glmnet
##
## Model fit template:
## glmnet::glmnet(x = missing_arg(), y = missing_arg(), weights = missing_arg(),
##     alpha = double(1), family = "poisson")
```

#### 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.

Predictors should have the same scale. One way to achieve this is to center and scale each so that each predictor has mean zero and a variance of one. By default, `glmnet::glmnet()` uses the argument `standardize = TRUE` to center and scale the data.

#### 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.

#### 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.

parsnip documentation built on June 24, 2024, 5:14 p.m.