formula {bayesbr} R Documentation

## Formula Variables

### Description

Transforming a formula object into a list with the variables and their names for the beta regression model of the bayesbr package.

### Usage

```formula(formula, data = NULL)
```

### Arguments

 `formula` symbolic description of the model (of type `y ~ x` or `y ~ x | z`;). `data` Data frame with regression observations

### Details

The form of the formula used for the `Bayesbr` package follows the pattern proposed in `Formula`. The expression y ~ represents that y is the response variable of the beta regression, everything to the right of the ~ operator represents covariates or intercepts for the parameter θ or ζ of the variable response .

The + operator adds one more explanatory covariate for the parameter,the operator : indicates interaction between variables adjacent to the operator, operator * adds the variables adjacent to the operator as covariable and the interaction between them the operator | represents that the next covariates are explanatory for ζ and those that were before the operator are explanatory for θ. So, in the formula `y ~ x1 + x2 | x3 + x4` x1 and x2 are the covariates for the parameter θ and x3 and x4 are the covariates of ζ. θ and ζ are parameters of the variable y answer. The numbers 1 and 0 represent, respectively, the presence or not of the intercept in the construction of the model. By default, the intercept is included, so the number 1 is necessary only when the user wants to include only the intercept for the estimation of the parameter in question. Here are some examples:

`y ~ 0 | x1`: No estimate for θ

`y ~ 1 | 0 + x2`: The estimation for θ will be made only with the intercept, and the estimation for ζ will not use the intercept only the covariable x2

`y~ x3*x4 | x5:x6`: The estimation for θ will be with the covariables `x3` and `x4` and the interaction between them, and the estimation for ζ will be the interaction between variables `x5` and `x6`.

The variables passed to the formula can be environment variables or columns of a dataframe, in which case the dataframe must be informed.

### Value

A list containing the following items:

Y

A vector containing the model response variable,

X

A matrix containing the covariates for theta of the model,

W

A matrix containing the covariates of the model for zeta

name_y

The name passed in the call to the `bayesbr` function for the variable response,

name_x

The name passed in the call to the `bayesbr` function for the covariates for theta,

name_w

The name passed in the call to the `bayesbr` function for covariates for zeta.

### See Also

`bayesbr`

[Package bayesbr version 0.0.1.0 Index]