# prior_fr: prior_fr In SVA-SE/freedom: Demonstration of Disease Freedom (DDF)

 prior_fr R Documentation

## prior_fr

### Description

Calculate the prior probability of freedom (year = k)

### Usage

```prior_fr(post_fr, intro)
```

### Arguments

 `post_fr` The posterior probability of freedom (year = k-1) `intro` The annual probability of introduction

### Details

In order to calculate the posterior probability of freedom (year = k) , the prior probability of freedom (year = k) is first calculated from the posterior probability of freedom (year = k-1) from the previous year and the annual probability that the disease is introduced into the population.

### Value

A vector. The prior probability of freedom (year = k)

### Examples

```## Calculate the posterior probability of freedom after applying a
## sensitivity to a prior probability of freedom:
post_pf <- post_fr(0.5, 0.4)
## Then discount the probability of introduction (0.05) from the
## posterior probability of freedom to calculate the subsequent
## prior probability of freedom for the next time step:
prior_pf <- prior_fr(post_pf, 0.05)
```

SVA-SE/freedom documentation built on Feb. 1, 2023, 5:50 p.m.