README.Rmd

---
title: "OpenWAR"
output:
  github_document:
    html_preview: true
---

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### An open-source system for computing Wins Above Replacement

This package is designed to present a reference implementation of [Wins Above Replacement](http://en.wikipedia.org/wiki/Wins_above_replacement) for Major League Baseball players. 

#### Installation

The **Sxslt** package is required in order to download new game data from MLBAM. This package is not present on CRAN. Hence, some manual installation may be necessary. The following command:

```{r, eval=FALSE}
devtools::install_github("omegahat/Sxslt")
```

should do the trick. If it doesn't please check that your operating system meets the `SystemRequirements`. These can be installed on Ubuntu by:

```{bash, eval=FALSE}
sudo apt-get install libxslt1-dev libxslt1.1 libxml2 libxml2-dev
```

Next, installing **openWAR** is best accomplished through the *install_github* function in the **devtools** package. 

```{r, eval=FALSE}
devtools::install_github("beanumber/openWAR")
```

#### Data Source

The *gameday* function downloads play-by-play data from the GameDay server hosted by Major League Baseball Advanced Media. This data is not *libre*, but it lives on a publicly-available webserver. 

Getting individual game data is as simple as:

```{r}
library(openWAR)
gd <- gameday()
summary(gd)
plot(gd)
```

To retrieve a `data.frame` of many games worth, try:

```{r, eval=FALSE}
ds <- getData()
```

This will retrieve play-by-play data for all games played yesterday (by default). For each play, 62 variables are recorded. 

#### Methodology

Please see our full paper on the [arXiv](http://arxiv.org/abs/1312.7158) or in [*Journal of Quantitative Analysis in Sports*](https://www.degruyter.com/view/j/jqas.2015.11.issue-2/jqas-2014-0098/jqas-2014-0098.xml).