---
title: "Demographic Inference with Jaatha"
author: "Paul Staab"
date: "jaatha `r packageVersion('jaatha')`"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Using Jaatha for Demographic Inference}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

When used for demographic inference, Jaatha supports using the package `coala` 
as simulation engine. If these packages do not suit your needs, it is of course 
also possible to use the normal interface described in the `Introduction` 
vignette.


Creating a Model
----------------
Jaatha automatically creates a simulation function, parameter ranges and 
summary statistics from a `coala` model. We can for example specify a simple 
isolation-with-migration model using `par_range`s to mark parameters we want
to estimate with Jaatha: 

```{r}
if(require("coala")) {	
   model <- coal_model(c(10, 15), 100) +
      feat_mutation(par_range("theta", 1, 10)) +
      feat_migration(par_range("m", 0, 3), symmetric = TRUE) +
      feat_pop_merge(par_range("t_split", 0.1, 2), 2, 1) + 
      feat_recombination(1) +
      sumstat_jsfs()
}	
```

We can now just pass this `coala` model to the `create_jaatha_model` function
to convert it into a Jaatha model:

```{r}
if(requireNamespace("coala")) {
     library(jaatha)
     jaatha_model <- create_jaatha_model(model)
}
```

This uses `coala` for the simulations, gets the parameter ranges specified with
`par_range` and uses summary statistics added to the model.
Coala supports a wide range of models. Please refer to its documentation for
more information.

Importing Data
--------------
You can use coala's `calc_sumstats_form_data` function to calculate the summary
statistic for genetic data. The output of this function can be directly passed
on to `create_jaatha_data`.

Running Jaatha
--------------
From here on, you can estimate parameters using the `jaatha` as described in the
introduction vignette. 

If you are using a simulator that is writing temporary
files to disk (e.g. `ms`, `msms` and `seq-gen`), please make sure that there
is sufficient free space on your `tempdir()` to store the output of `sim` 
simulations per core that you use (arguments `sim` and `cores` in the `jaatha`
function). Also, please make sure that your machine does not run out of memory.
Both will lead to failtures during the estimation process. Reducing the number
of cores reduces both the required memory and disk space at the cost of a 
longer runtime.