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<title>Dutilleul moving window bivariate raster correlation — raster.modified.ttest • spatialEco</title>


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<meta property="og:title" content="Dutilleul moving window bivariate raster correlation — raster.modified.ttest" />
<meta property="og:description" content="A bivarate raster correlation using Dutilleul's 
             modified t-test
This function provides a bivariate moving window correlation using the modified  
t-test to account for spatial autocorrelation. Point based subsampling is provided 
for computation tractability. The hexagon sampling is recommended as it it good  
at capturing spatial process that includes nonstationarity and anistropy." />




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    <h1>Dutilleul moving window bivariate raster correlation</h1>
    <small class="dont-index">Source: <a href='https://github.com/jeffreyevans/spatialEco/blob/master/R/raster.modified.ttest.R'><code>R/raster.modified.ttest.R</code></a></small>
    <div class="hidden name"><code>raster.modified.ttest.Rd</code></div>
    </div>

    <div class="ref-description">
    <p>A bivarate raster correlation using Dutilleul's 
             modified t-test</p>
<p>This function provides a bivariate moving window correlation using the modified  
t-test to account for spatial autocorrelation. Point based subsampling is provided 
for computation tractability. The hexagon sampling is recommended as it it good  
at capturing spatial process that includes nonstationarity and anistropy.</p>
    </div>

    <pre class="usage"><span class='fu'>raster.modified.ttest</span><span class='op'>(</span>
  <span class='va'>x</span>,
  <span class='va'>y</span>,
  x.idx <span class='op'>=</span> <span class='fl'>1</span>,
  y.idx <span class='op'>=</span> <span class='fl'>1</span>,
  d <span class='op'>=</span> <span class='st'>"AUTO"</span>,
  sub.sample <span class='op'>=</span> <span class='cn'>FALSE</span>,
  type <span class='op'>=</span> <span class='st'>"hexagon"</span>,
  p <span class='op'>=</span> <span class='fl'>0.1</span>,
  size <span class='op'>=</span> <span class='cn'>NULL</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>x</th>
      <td><p>x raster for correlation, SpatialPixelsDataFrame or 
SpatialGridDataFrame object</p></td>
    </tr>
    <tr>
      <th>y</th>
      <td><p>y raster for correlation, SpatialPixelsDataFrame or 
SpatialGridDataFrame object</p></td>
    </tr>
    <tr>
      <th>x.idx</th>
      <td><p>Index for the column in the x raster object</p></td>
    </tr>
    <tr>
      <th>y.idx</th>
      <td><p>Index for the column in the y raster object</p></td>
    </tr>
    <tr>
      <th>d</th>
      <td><p>Distance for finding neighbors</p></td>
    </tr>
    <tr>
      <th>sub.sample</th>
      <td><p>Should a sub-sampling approach be employed (TRUE/FALSE)</p></td>
    </tr>
    <tr>
      <th>type</th>
      <td><p>If sub.sample = TRUE, what type of sample (random  or hexagon)</p></td>
    </tr>
    <tr>
      <th>p</th>
      <td><p>If sub.sample = TRUE, what proportion of population 
should be sampled</p></td>
    </tr>
    <tr>
      <th>size</th>
      <td><p>Fixed sample size</p></td>
    </tr>
    </table>

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

    <p>A SpatialPixelsDataFrame or SpatialPointsDataFrame with the 
        following attributes:</p><ul>
<li><p>corr        Correlation</p></li>
<li><p>Fstat       The F-statistic calculated as [degrees of freedom * 
                    unscaled F-statistic]</p></li>
<li><p>p.value     p-value for the test</p></li>
<li><p>moran.x     Moran's-I for x</p></li>
<li><p>moran.y     Moran's-I for y</p></li>
</ul>

    <h2 class="hasAnchor" id="references"><a class="anchor" href="#references"></a>References</h2>

    <p>Clifford, P., S. Richardson, D. Hemon (1989), Assessing the significance of the  
  correlationbetween two spatial processes. Biometrics 45:123-134.</p>
<p>Dutilleul, P. (1993), Modifying the t test for assessing the correlation between 
  two spatial processes. Biometrics 49:305-314.</p>
    <h2 class="hasAnchor" id="see-also"><a class="anchor" href="#see-also"></a>See also</h2>

    <div class='dont-index'><p><code><a href='https://rdrr.io/pkg/SpatialPack/man/modified.ttest.html'>modified.ttest</a></code> for test details</p></div>
    <h2 class="hasAnchor" id="author"><a class="anchor" href="#author"></a>Author</h2>

    <p>Jeffrey S. Evans  &lt;jeffrey_evans@tnc.org&gt;</p>

    <h2 class="hasAnchor" id="examples"><a class="anchor" href="#examples"></a>Examples</h2>
    <pre class="examples"><div class='input'><span class='kw'>if</span> <span class='op'>(</span><span class='cn'>FALSE</span><span class='op'>)</span> <span class='op'>{</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://github.com/r-spatial/gstat/'>gstat</a></span><span class='op'>)</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://github.com/edzer/sp/'>sp</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'>meuse</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'>meuse.grid</span><span class='op'>)</span>                                       
<span class='fu'><a href='https://rdrr.io/pkg/sp/man/coordinates.html'>coordinates</a></span><span class='op'>(</span><span class='va'>meuse</span><span class='op'>)</span> <span class='op'>&lt;-</span> <span class='op'>~</span><span class='va'>x</span> <span class='op'>+</span> <span class='va'>y</span>                           
<span class='fu'><a href='https://rdrr.io/pkg/sp/man/coordinates.html'>coordinates</a></span><span class='op'>(</span><span class='va'>meuse.grid</span><span class='op'>)</span> <span class='op'>&lt;-</span> <span class='op'>~</span><span class='va'>x</span> <span class='op'>+</span> <span class='va'>y</span>                      
                                                        
<span class='co'># GRID-1 log(copper):                                              </span>
<span class='va'>v1</span> <span class='op'>&lt;-</span> <span class='fu'><a href='https://rdrr.io/pkg/gstat/man/variogram.html'>variogram</a></span><span class='op'>(</span><span class='fu'><a href='https://rdrr.io/r/base/Log.html'>log</a></span><span class='op'>(</span><span class='va'>copper</span><span class='op'>)</span> <span class='op'>~</span> <span class='fl'>1</span>, <span class='va'>meuse</span><span class='op'>)</span>                  
<span class='va'>x1</span> <span class='op'>&lt;-</span> <span class='fu'><a href='https://rdrr.io/pkg/gstat/man/fit.variogram.html'>fit.variogram</a></span><span class='op'>(</span><span class='va'>v1</span>, <span class='fu'><a href='https://rdrr.io/pkg/gstat/man/vgm.html'>vgm</a></span><span class='op'>(</span><span class='fl'>1</span>, <span class='st'>"Sph"</span>, <span class='fl'>800</span>, <span class='fl'>1</span><span class='op'>)</span><span class='op'>)</span>           
<span class='va'>G1</span> <span class='op'>&lt;-</span> <span class='fu'><a href='https://rdrr.io/pkg/gstat/man/krige.html'>krige</a></span><span class='op'>(</span><span class='va'>zinc</span> <span class='op'>~</span> <span class='fl'>1</span>, <span class='va'>meuse</span>, <span class='va'>meuse.grid</span>, <span class='va'>x1</span>, nmax <span class='op'>=</span> <span class='fl'>30</span><span class='op'>)</span>
<span class='fu'><a href='https://rdrr.io/pkg/sp/man/gridded-methods.html'>gridded</a></span><span class='op'>(</span><span class='va'>G1</span><span class='op'>)</span> <span class='op'>&lt;-</span> <span class='cn'>TRUE</span>                                      
<span class='va'>G1</span><span class='op'>@</span><span class='va'>data</span> <span class='op'>=</span> <span class='fu'><a href='https://rdrr.io/pkg/raster/man/as.data.frame.html'>as.data.frame</a></span><span class='op'>(</span><span class='va'>G1</span><span class='op'>@</span><span class='va'>data</span><span class='op'>[</span>,<span class='op'>-</span><span class='fl'>2</span><span class='op'>]</span><span class='op'>)</span>

<span class='co'># GRID-2 log(elev):                                              </span>
<span class='va'>v2</span> <span class='op'>&lt;-</span> <span class='fu'><a href='https://rdrr.io/pkg/gstat/man/variogram.html'>variogram</a></span><span class='op'>(</span><span class='fu'><a href='https://rdrr.io/r/base/Log.html'>log</a></span><span class='op'>(</span><span class='va'>elev</span><span class='op'>)</span> <span class='op'>~</span> <span class='fl'>1</span>, <span class='va'>meuse</span><span class='op'>)</span>                  
<span class='va'>x2</span> <span class='op'>&lt;-</span> <span class='fu'><a href='https://rdrr.io/pkg/gstat/man/fit.variogram.html'>fit.variogram</a></span><span class='op'>(</span><span class='va'>v2</span>, <span class='fu'><a href='https://rdrr.io/pkg/gstat/man/vgm.html'>vgm</a></span><span class='op'>(</span><span class='fl'>.1</span>, <span class='st'>"Sph"</span>, <span class='fl'>1000</span>, <span class='fl'>.6</span><span class='op'>)</span><span class='op'>)</span>        
<span class='va'>G2</span> <span class='op'>&lt;-</span> <span class='fu'><a href='https://rdrr.io/pkg/gstat/man/krige.html'>krige</a></span><span class='op'>(</span><span class='va'>elev</span> <span class='op'>~</span> <span class='fl'>1</span>, <span class='va'>meuse</span>, <span class='va'>meuse.grid</span>, <span class='va'>x2</span>, nmax <span class='op'>=</span> <span class='fl'>30</span><span class='op'>)</span>
<span class='fu'><a href='https://rdrr.io/pkg/sp/man/gridded-methods.html'>gridded</a></span><span class='op'>(</span><span class='va'>G2</span><span class='op'>)</span> <span class='op'>&lt;-</span> <span class='cn'>TRUE</span>    
<span class='va'>G2</span><span class='op'>@</span><span class='va'>data</span> <span class='op'>&lt;-</span> <span class='fu'><a href='https://rdrr.io/pkg/raster/man/as.data.frame.html'>as.data.frame</a></span><span class='op'>(</span><span class='va'>G2</span><span class='op'>@</span><span class='va'>data</span><span class='op'>[</span>,<span class='op'>-</span><span class='fl'>2</span><span class='op'>]</span><span class='op'>)</span>
<span class='va'>G2</span><span class='op'>@</span><span class='va'>data</span><span class='op'>[</span>,<span class='fl'>1</span><span class='op'>]</span> <span class='op'>&lt;-</span> <span class='va'>G2</span><span class='op'>@</span><span class='va'>data</span><span class='op'>[</span>,<span class='fl'>1</span><span class='op'>]</span>

<span class='va'>corr</span> <span class='op'>&lt;-</span> <span class='fu'>raster.modifed.ttest</span><span class='op'>(</span><span class='va'>G1</span>, <span class='va'>G2</span><span class='op'>)</span>
  <span class='fu'><a href='https://rdrr.io/pkg/raster/man/plot.html'>plot</a></span><span class='op'>(</span><span class='fu'>raster</span><span class='fu'>::</span><span class='fu'><a href='https://rdrr.io/pkg/raster/man/raster.html'>raster</a></span><span class='op'>(</span><span class='va'>corr</span>,<span class='fl'>1</span><span class='op'>)</span><span class='op'>)</span>
  
<span class='va'>corr.rand</span> <span class='op'>&lt;-</span> <span class='fu'>raster.modifed.ttest</span><span class='op'>(</span><span class='va'>G1</span>, <span class='va'>G2</span>, sub.sample <span class='op'>=</span> <span class='cn'>TRUE</span>, type <span class='op'>=</span> <span class='st'>"random"</span><span class='op'>)</span>   
<span class='va'>corr.hex</span> <span class='op'>&lt;-</span> <span class='fu'>raster.modifed.ttest</span><span class='op'>(</span><span class='va'>G1</span>, <span class='va'>G2</span>, sub.sample <span class='op'>=</span> <span class='cn'>TRUE</span>, d <span class='op'>=</span> <span class='fl'>500</span>, size <span class='op'>=</span> <span class='fl'>1000</span><span class='op'>)</span>  
  <span class='fu'><a href='https://rdrr.io/pkg/raster/man/headtail.html'>head</a></span><span class='op'>(</span><span class='va'>corr.hex</span><span class='op'>@</span><span class='va'>data</span><span class='op'>)</span>
    <span class='fu'><a href='https://rdrr.io/pkg/sp/man/bubble.html'>bubble</a></span><span class='op'>(</span><span class='va'>corr.hex</span>, <span class='st'>"corr"</span><span class='op'>)</span> 
<span class='op'>}</span>

</div></pre>
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