<!-- Generated by pkgdown: do not edit by hand -->
<!DOCTYPE html>
<html lang="en">
  <head>
  <meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">

<title>Terrain Ruggedness Index — tri • spatialEco</title>


<!-- jquery -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js" integrity="sha256-CSXorXvZcTkaix6Yvo6HppcZGetbYMGWSFlBw8HfCJo=" crossorigin="anonymous"></script>
<!-- Bootstrap -->

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.4.1/css/bootstrap.min.css" integrity="sha256-bZLfwXAP04zRMK2BjiO8iu9pf4FbLqX6zitd+tIvLhE=" crossorigin="anonymous" />

<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.4.1/js/bootstrap.min.js" integrity="sha256-nuL8/2cJ5NDSSwnKD8VqreErSWHtnEP9E7AySL+1ev4=" crossorigin="anonymous"></script>

<!-- bootstrap-toc -->
<link rel="stylesheet" href="../bootstrap-toc.css">
<script src="../bootstrap-toc.js"></script>

<!-- Font Awesome icons -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.12.1/css/all.min.css" integrity="sha256-mmgLkCYLUQbXn0B1SRqzHar6dCnv9oZFPEC1g1cwlkk=" crossorigin="anonymous" />
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.12.1/css/v4-shims.min.css" integrity="sha256-wZjR52fzng1pJHwx4aV2AO3yyTOXrcDW7jBpJtTwVxw=" crossorigin="anonymous" />

<!-- clipboard.js -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/clipboard.js/2.0.6/clipboard.min.js" integrity="sha256-inc5kl9MA1hkeYUt+EC3BhlIgyp/2jDIyBLS6k3UxPI=" crossorigin="anonymous"></script>

<!-- headroom.js -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/headroom/0.11.0/headroom.min.js" integrity="sha256-AsUX4SJE1+yuDu5+mAVzJbuYNPHj/WroHuZ8Ir/CkE0=" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/headroom/0.11.0/jQuery.headroom.min.js" integrity="sha256-ZX/yNShbjqsohH1k95liqY9Gd8uOiE1S4vZc+9KQ1K4=" crossorigin="anonymous"></script>

<!-- pkgdown -->
<link href="../pkgdown.css" rel="stylesheet">
<script src="../pkgdown.js"></script>




<meta property="og:title" content="Terrain Ruggedness Index — tri" />
<meta property="og:description" content="Implementation of the Riley et al (1999) Terrain Ruggedness Index
The algebraic approximation is considerably faster. However, because
inclusion of the center cell, the larger the scale the larger the divergence
of the minimum value.
Recommended ranges for classifying Topographic Ruggedness Index:
0-80 - level terrain surface.
81-116 - nearly level surface.
117-161 - slightly rugged surface.
162-239 - intermediately rugged surface.
240-497 - moderately rugged surface.
498-958 - highly rugged surface.
gt 959 - extremely rugged surface.

" />




<!-- mathjax -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js" integrity="sha256-nvJJv9wWKEm88qvoQl9ekL2J+k/RWIsaSScxxlsrv8k=" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/config/TeX-AMS-MML_HTMLorMML.js" integrity="sha256-84DKXVJXs0/F8OTMzX4UR909+jtl4G7SPypPavF+GfA=" crossorigin="anonymous"></script>

<!--[if lt IE 9]>
<script src="https://oss.maxcdn.com/html5shiv/3.7.3/html5shiv.min.js"></script>
<script src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script>
<![endif]-->



  </head>

  <body data-spy="scroll" data-target="#toc">
    <div class="container template-reference-topic">
      <header>
      <div class="navbar navbar-default navbar-fixed-top" role="navigation">
  <div class="container">
    <div class="navbar-header">
      <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false">
        <span class="sr-only">Toggle navigation</span>
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
        <span class="icon-bar"></span>
      </button>
      <span class="navbar-brand">
        <a class="navbar-link" href="../index.html">spatialEco</a>
        <span class="version label label-default" data-toggle="tooltip" data-placement="bottom" title="Released version">1.3-7</span>
      </span>
    </div>

    <div id="navbar" class="navbar-collapse collapse">
      <ul class="nav navbar-nav">
        <li>
  <a href="../index.html">
    <span class="fas fa-home fa-lg"></span>
     
  </a>
</li>
<li>
  <a href="../reference/index.html">Reference</a>
</li>
      </ul>
      <ul class="nav navbar-nav navbar-right">
        <li>
  <a href="https://github.com/jeffreyevans/spatialEco/">
    <span class="fab fa-github fa-lg"></span>
     
  </a>
</li>
      </ul>
      
    </div><!--/.nav-collapse -->
  </div><!--/.container -->
</div><!--/.navbar -->

      

      </header>

<div class="row">
  <div class="col-md-9 contents">
    <div class="page-header">
    <h1>Terrain Ruggedness Index</h1>
    <small class="dont-index">Source: <a href='https://github.com/jeffreyevans/spatialEco/blob/master/R/tri.R'><code>R/tri.R</code></a></small>
    <div class="hidden name"><code>tri.Rd</code></div>
    </div>

    <div class="ref-description">
    <p>Implementation of the Riley et al (1999) Terrain Ruggedness Index</p>
<p>The algebraic approximation is considerably faster. However, because
inclusion of the center cell, the larger the scale the larger the divergence
of the minimum value.</p>
<p>Recommended ranges for classifying Topographic Ruggedness Index:</p><ul>
<li><p>0-80 - level terrain surface.</p></li>
<li><p>81-116 - nearly level surface.</p></li>
<li><p>117-161 - slightly rugged surface.</p></li>
<li><p>162-239 - intermediately rugged surface.</p></li>
<li><p>240-497 - moderately rugged surface.</p></li>
<li><p>498-958 - highly rugged surface.</p></li>
<li><p>gt 959 - extremely rugged surface.</p></li>
</ul>

    </div>

    <pre class="usage"><span class='fu'>tri</span><span class='op'>(</span><span class='va'>r</span>, s <span class='op'>=</span> <span class='fl'>3</span>, exact <span class='op'>=</span> <span class='cn'>TRUE</span>, file.name <span class='op'>=</span> <span class='cn'>NULL</span>, <span class='va'>...</span><span class='op'>)</span></pre>

    <h2 class="hasAnchor" id="arguments"><a class="anchor" href="#arguments"></a>Arguments</h2>
    <table class="ref-arguments">
    <colgroup><col class="name" /><col class="desc" /></colgroup>
    <tr>
      <th>r</th>
      <td><p>RasterLayer class object</p></td>
    </tr>
    <tr>
      <th>s</th>
      <td><p>Scale of window. Must be odd number, can represent 2
dimensions (eg., s=c(3,5) would represent a 3 x 5 window)</p></td>
    </tr>
    <tr>
      <th>exact</th>
      <td><p>Calculate (TRUE/FALSE) the exact TRI or an algebraic
approximation.</p></td>
    </tr>
    <tr>
      <th>file.name</th>
      <td><p>Name of output raster (optional)</p></td>
    </tr>
    <tr>
      <th>...</th>
      <td><p>Additional arguments passed to writeRaster</p></td>
    </tr>
    </table>

    <h2 class="hasAnchor" id="value"><a class="anchor" href="#value"></a>Value</h2>

    <p>raster class object or raster written to disk</p>
    <h2 class="hasAnchor" id="references"><a class="anchor" href="#references"></a>References</h2>

    <p>Riley, S.J., S.D. DeGloria and R. Elliot (1999) A terrain
ruggedness index that quantifies topographic heterogeneity,
Intermountain Journal of Sciences 5(1-4):23-27.</p>
    <h2 class="hasAnchor" id="author"><a class="anchor" href="#author"></a>Author</h2>

    <p>Jeffrey S. Evans  <a href='mailto:jeffrey_evans@tnc.org'>jeffrey_evans@tnc.org</a></p>

    <h2 class="hasAnchor" id="examples"><a class="anchor" href="#examples"></a>Examples</h2>
    <pre class="examples"><div class='input'><span class='co'># \donttest{</span>
 <span class='kw'><a href='https://rdrr.io/r/base/library.html'>library</a></span><span class='op'>(</span><span class='va'><a href='https://rspatial.org/raster'>raster</a></span><span class='op'>)</span>
 <span class='fu'><a href='https://rdrr.io/r/utils/data.html'>data</a></span><span class='op'>(</span><span class='va'>elev</span><span class='op'>)</span>
  <span class='op'>(</span> <span class='va'>tri.ext</span> <span class='op'>&lt;-</span> <span class='fu'>tri</span><span class='op'>(</span><span class='va'>elev</span><span class='op'>)</span> <span class='op'>)</span>
</div><div class='output co'>#&gt; class      : RasterLayer 
#&gt; dimensions : 6, 6, 36  (nrow, ncol, ncell)
#&gt; resolution : 0.5, 0.5  (x, y)
#&gt; extent     : -1.5, 1.5, -1.5, 1.5  (xmin, xmax, ymin, ymax)
#&gt; crs        : +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0 
#&gt; source     : memory
#&gt; names      : layer 
#&gt; values     : 14.89966, 14.89966  (min, max)
#&gt; </div><div class='input'>  <span class='op'>(</span> <span class='va'>tri.app</span> <span class='op'>&lt;-</span> <span class='fu'>tri</span><span class='op'>(</span><span class='va'>elev</span>, exact <span class='op'>=</span> <span class='cn'>FALSE</span><span class='op'>)</span> <span class='op'>)</span>
</div><div class='output co'>#&gt; class      : RasterLayer 
#&gt; dimensions : 6, 6, 36  (nrow, ncol, ncell)
#&gt; resolution : 0.5, 0.5  (x, y)
#&gt; extent     : -1.5, 1.5, -1.5, 1.5  (xmin, xmax, ymin, ymax)
#&gt; crs        : +proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0 
#&gt; source     : memory
#&gt; names      : layer 
#&gt; values     : 14.89966, 14.89966  (min, max)
#&gt; </div><div class='input'>  <span class='fu'><a href='https://rdrr.io/pkg/raster/man/plot.html'>plot</a></span><span class='op'>(</span><span class='fu'><a href='https://rdrr.io/pkg/raster/man/stack.html'>stack</a></span><span class='op'>(</span><span class='va'>tri.ext</span>, <span class='va'>tri.app</span><span class='op'>)</span><span class='op'>)</span>
</div><div class='img'><img src='tri-1.png' alt='' width='700' height='433' /></div><div class='input'><span class='co'># }</span>

</div></pre>
  </div>
  <div class="col-md-3 hidden-xs hidden-sm" id="pkgdown-sidebar">
    <nav id="toc" data-toggle="toc" class="sticky-top">
      <h2 data-toc-skip>Contents</h2>
    </nav>
  </div>
</div>


      <footer>
      <div class="copyright">
  <p>Developed by Jeffrey S. Evans.</p>
</div>

<div class="pkgdown">
  <p>Site built with <a href="https://pkgdown.r-lib.org/">pkgdown</a> 1.6.1.</p>
</div>

      </footer>
   </div>

  


  </body>
</html>


