prior {bayesplay} R Documentation

## Specify a prior

### Description

Define priors using different different distribution families

### Usage

```prior(family, ...)
```

### Arguments

 `family` the prior distribution (see details) `...` see details

### Details

#### Available distribution families

The following distributions families can be used for the prior

• `normal` a normal distribution

• `student_t` a scaled and shifted t-distribution

• `cauchy` a Cauchy distribution

• `uniform` a uniform distribution

• `point` a point

• `beta` a beta distribution The parameters that need to be specified will be dependent on the family

#### Normal distribution

When `family` is set to `normal` then the following parameters may be be set

• `mean` mean of the normal prior

• `sd` standard deviation of the normal prior

• `range` (optional) a vector specifying the parameter range

#### Student t distribution

When `family` is set to `student_t` then the following parameters may be set

• `mean` mean of the scaled and shifted t prior

• `sd` standard deviation of the scaled and shifted t prior

• `df` degrees of freedom of the scaled and shifted t prior

• `range` (optional) a vector specifying the parameter range

#### Cauchy distribution

When `family` is set to `cauchy` then the following parameters may be set

• `location` the centre of the Cauchy distribution (default: 0)

• `scale` the scale of the Cauchy distribution

• `range` (optional) a vector specifying the parameter range

#### Uniform distribution

When `family` is set to `uniform` then the following parameters must be set

• `min` the lower bound

• `max` the upper bound

#### Point

When `family` is set to `point` then the following parameters may be set

• `point` the location of the point prior (default: 0)

#### Beta

When `family` is set to `beta` then the following parameters may be set

• `alpha` the first shape parameter

• `beta` the second shape parameter

### Value

an object of class `prior`

### Examples

```
# specify a normal prior
prior(family = "normal", mean = 0, sd = 13.3)

# specify a half-normal (range 0 to Infinity) prior
prior(family = "normal", mean = 0, sd = 13.3, range = c(0, Inf))

# specify a student t prior
prior(family = "student_t", mean = 0, sd = 13.3, df = 79)

# specify a truncated t prior
prior(family = "student_t", mean = 0, sd = 13.3, df = 79, range = c(-40, 40))

# specify a cauchy prior
prior(family = "cauchy", location = 0, scale = .707)

# specify a half cauchy prior
prior(family = "cauchy", location = 0, scale = 1, range = c(-Inf, 0))

# specify a uniform prior
prior(family = "uniform", min = 0, max = 20)

# specify a point prior
prior(family = "point", point = 0)

# specify a beta prior
prior(family = "beta", alpha = 2.5, beta = 3.8)
```

[Package bayesplay version 0.9.2 Index]