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<table width="100%" summary="page for aral"><tr><td>aral</td><td style="text-align: right;">R Documentation</td></tr></table>

<h2>Aral sea remote sensed chlorophyll data</h2>

<h3>Description</h3>

<p>SeaWifs satellite chlorophyll measurements for the 38th 8-day observation period of the year in the Aral sea, averaged over 1998-2002, along with an Aral sea boundary file. 
</p>


<h3>Usage</h3>

<pre>
data(aral)
data(aral.bnd)
</pre>


<h3>Format</h3>

<p>The <code>aral</code> data frame has the following columns
</p>

<dl>
<dt>lon</dt><dd><p>longitude of pixel or boundary vertex.</p>
</dd>
<dt>lat</dt><dd><p>latitude of pixel or boundary vertex.</p>
</dd>
<dt>chl</dt><dd><p>chlorophyll measurement</p>
</dd>
<dt>exra</dt><dd><p>The highest rainfall observed in any 12 hour period in that year, in mm. </p>
</dd>
</dl>


<h3>Details</h3>

<p>Trying to smooth the data with a conventional smoother, such as a thin plate spline, leads to linkage between the two arms of the sea, which is clearly an artefact. A soap film smoother avoids this problem.
</p>


<h3>Source</h3>

<p><a href="https://seawifs.gsfc.nasa.gov/">https://seawifs.gsfc.nasa.gov/</a>
</p>


<h3>Examples</h3>

<pre>
require(gamair);require(mgcv)
data(aral); data(aral.bnd)

## define some knots...
knt &lt;- list(lon=c(58.55,59.09,59.36,59.64,59.91,60.18,58.27,58.55,59.09,
59.36,59.64,59.91,60.18,60.45,58.27,58.55,58.82,59.09,59.36,59.64,59.91,
60.18,60.45,58.27,58.55,59.36,59.64,59.91,60.18,58.55,59.36,59.64,59.91,
60.18,58.55,58.82,59.36,59.64,59.91,60.18,60.45,58.82,59.09,59.64,59.91,
60.18,59.64),
lat=c(44.27,44.27,44.27,44.27,44.27,44.27,44.55,44.55,44.55,44.55,44.55,
44.55,44.55,44.55,44.82,44.82,44.82,44.82,44.82,44.82,44.82,44.82,44.82,
45.09,45.09,45.09,45.09,45.09,45.09,45.36,45.36,45.36,45.36,45.36,45.64,
45.64,45.64,45.64,45.64,45.64,45.64,45.91,45.91,45.91,45.91,45.91,46.18))

## fit soap film...
b &lt;-  gam(chl~s(lon,lat,k=30,bs="so",xt=list(bnd=list(aral.bnd),
                nmax=150)),knots=knt,data=aral)

## plot results...
plot(b)
</pre>


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