expand_df {aggTrees} | R Documentation |

## Covariate Matrix Expansion

### Description

Expands the covariate matrix, adding interactions and polynomials. This is particularly useful for penalized regressions.

### Usage

```
expand_df(X, int_order = 2, poly_order = 4, threshold = 0)
```

### Arguments

`X` |
Covariate matrix (no intercept). |

`int_order` |
Order of interactions to be added. Set equal to one if no interactions are desired. |

`poly_order` |
Order of the polynomials to be added. Set equal to one if no polynomials are desired. |

`threshold` |
Drop binary variables representing less than |

### Details

`expand_df`

assumes that categorical variables are coded as `factors`

. Also, no missing values are allowed.

`expand_df`

uses `model.matrix`

to expand factors to a set of dummy variables. Then, it identifies continuous covariates as those
not having 0 and 1 as unique values.

`expand_df`

first introduces all the `int_order`

-way interactions between the variables (using the expanded set of dummies), and then adds
`poly_order`

-order polynomials for continuous covariates.

### Value

The expanded covariate matrix, as a data frame.

### Author(s)

Riccardo Di Francesco

*aggTrees*version 2.0.2 Index]