# density_ratio: Compute Density Ratios In brms: Bayesian Regression Models using 'Stan'

 density_ratio R Documentation

## Compute Density Ratios

### Description

Compute the ratio of two densities at given points based on draws of the corresponding distributions.

### Usage

``````density_ratio(x, y = NULL, point = 0, n = 4096, ...)
``````

### Arguments

 `x` Vector of draws from the first distribution, usually the posterior distribution of the quantity of interest. `y` Optional vector of draws from the second distribution, usually the prior distribution of the quantity of interest. If `NULL` (the default), only the density of `x` will be evaluated. `point` Numeric values at which to evaluate and compare the densities. Defaults to `0`. `n` Single numeric value. Influences the accuracy of the density estimation. See `density` for details. `...` Further arguments passed to `density`.

### Details

In order to achieve sufficient accuracy in the density estimation, more draws than usual are required. That is you may need an effective sample size of 10,000 or more to reliably estimate the densities.

### Value

A vector of length equal to `length(point)`. If `y` is provided, the density ratio of `x` against `y` is returned. Else, only the density of `x` is returned.

### Examples

``````x <- rnorm(10000)
y <- rnorm(10000, mean = 1)
density_ratio(x, y, point = c(0, 1))

``````

brms documentation built on Sept. 26, 2023, 1:08 a.m.