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      <h1>Add a Scalebar to a Map</h1>
      <small class="dont-index">Source: <a href="https://github.com/dankelley/oce/blob/HEAD/R/map.R" class="external-link"><code>R/map.R</code></a></small>
      <div class="d-none name"><code>mapScalebar.Rd</code></div>
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    <div class="ref-description section level2">
    <p>Draw a scalebar on a map created by <code><a href="mapPlot.html">mapPlot()</a></code> or otherwise.</p>
    </div>

    <div class="section level2">
    <h2 id="ref-usage">Usage<a class="anchor" aria-label="anchor" href="#ref-usage"></a></h2>
    <div class="sourceCode"><pre class="sourceCode r"><code><span><span class="fu">mapScalebar</span><span class="op">(</span></span>
<span>  <span class="va">x</span>,</span>
<span>  y <span class="op">=</span> <span class="cn">NULL</span>,</span>
<span>  <span class="va">length</span>,</span>
<span>  lwd <span class="op">=</span> <span class="fl">1.5</span> <span class="op">*</span> <span class="fu"><a href="https://rdrr.io/r/graphics/par.html" class="external-link">par</a></span><span class="op">(</span><span class="st">"lwd"</span><span class="op">)</span>,</span>
<span>  cex <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/graphics/par.html" class="external-link">par</a></span><span class="op">(</span><span class="st">"cex"</span><span class="op">)</span>,</span>
<span>  col <span class="op">=</span> <span class="st">"black"</span></span>
<span><span class="op">)</span></span></code></pre></div>
    </div>

    <div class="section level2">
    <h2 id="arguments">Arguments<a class="anchor" aria-label="anchor" href="#arguments"></a></h2>


<dl><dt id="arg-x-y">x, y<a class="anchor" aria-label="anchor" href="#arg-x-y"></a></dt>
<dd><p>position of the scalebar.  Eventually this may be similar to
the corresponding arguments in <code><a href="https://rdrr.io/r/graphics/legend.html" class="external-link">legend()</a></code>, but at the moment
<code>y</code> must be <code>NULL</code> and <code>x</code> must be <code>"topleft"</code> or <code>"topright"</code>.</p></dd>


<dt id="arg-length">length<a class="anchor" aria-label="anchor" href="#arg-length"></a></dt>
<dd><p>the distance to indicate, in kilometres.  If not provided, a
reasonable choice is made, based on the existing plot.</p></dd>


<dt id="arg-lwd">lwd<a class="anchor" aria-label="anchor" href="#arg-lwd"></a></dt>
<dd><p>line width of the scalebar.</p></dd>


<dt id="arg-cex">cex<a class="anchor" aria-label="anchor" href="#arg-cex"></a></dt>
<dd><p>character expansion factor for the scalebar text.</p></dd>


<dt id="arg-col">col<a class="anchor" aria-label="anchor" href="#arg-col"></a></dt>
<dd><p>color of the scalebar.</p></dd>

</dl></div>
    <div class="section level2">
    <h2 id="details">Details<a class="anchor" aria-label="anchor" href="#details"></a></h2>
    <p>The scale is appropriate to the centre of the plot, and will become
increasingly inaccurate away from that spot, with the error depending on
the projection and the fraction of the earth that is shown.</p>
<p>Until December 2020, it was required that the map had been drawn by <code><a href="mapPlot.html">mapPlot()</a></code>,
but now it can be any diagram showing longitude and latitude in degrees.</p>
    </div>
    <div class="section level2">
    <h2 id="see-also">See also<a class="anchor" aria-label="anchor" href="#see-also"></a></h2>
    <div class="dont-index"><p>A map must first have been created with <code><a href="mapPlot.html">mapPlot()</a></code>.</p>
<p>Other functions related to maps:
<code><a href="formatPosition.html">formatPosition</a>()</code>,
<code><a href="lonlat2map.html">lonlat2map</a>()</code>,
<code><a href="lonlat2utm.html">lonlat2utm</a>()</code>,
<code><a href="map2lonlat.html">map2lonlat</a>()</code>,
<code><a href="mapArrows.html">mapArrows</a>()</code>,
<code><a href="mapAxis.html">mapAxis</a>()</code>,
<code><a href="mapContour.html">mapContour</a>()</code>,
<code><a href="mapCoordinateSystem.html">mapCoordinateSystem</a>()</code>,
<code><a href="mapDirectionField.html">mapDirectionField</a>()</code>,
<code><a href="mapGrid.html">mapGrid</a>()</code>,
<code><a href="mapImage.html">mapImage</a>()</code>,
<code><a href="mapLines.html">mapLines</a>()</code>,
<code><a href="mapLocator.html">mapLocator</a>()</code>,
<code><a href="mapLongitudeLatitudeXY.html">mapLongitudeLatitudeXY</a>()</code>,
<code><a href="mapPlot.html">mapPlot</a>()</code>,
<code><a href="mapPoints.html">mapPoints</a>()</code>,
<code><a href="mapPolygon.html">mapPolygon</a>()</code>,
<code><a href="mapText.html">mapText</a>()</code>,
<code><a href="mapTissot.html">mapTissot</a>()</code>,
<code><a href="oceCRS.html">oceCRS</a>()</code>,
<code><a href="oceProject.html">oceProject</a>()</code>,
<code><a href="shiftLongitude.html">shiftLongitude</a>()</code>,
<code><a href="usrLonLat.html">usrLonLat</a>()</code>,
<code><a href="utm2lonlat.html">utm2lonlat</a>()</code></p></div>
    </div>
    <div class="section level2">
    <h2 id="author">Author<a class="anchor" aria-label="anchor" href="#author"></a></h2>
    <p>Dan Kelley</p>
    </div>

    <div class="section level2">
    <h2 id="ref-examples">Examples<a class="anchor" aria-label="anchor" href="#ref-examples"></a></h2>
    <div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span><span class="co"># \donttest{</span></span></span>
<span class="r-in"><span><span class="kw"><a href="https://rdrr.io/r/base/library.html" class="external-link">library</a></span><span class="op">(</span><span class="va"><a href="https://dankelley.github.io/oce/">oce</a></span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/utils/data.html" class="external-link">data</a></span><span class="op">(</span><span class="va">coastlineWorld</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="co"># Arctic Ocean</span></span></span>
<span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/graphics/par.html" class="external-link">par</a></span><span class="op">(</span>mar <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="fl">2.5</span>, <span class="fl">2.5</span>, <span class="fl">1</span>, <span class="fl">1</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="fu"><a href="mapPlot.html">mapPlot</a></span><span class="op">(</span><span class="va">coastlineWorld</span>,</span></span>
<span class="r-in"><span>    latitudelim <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="fl">60</span>, <span class="fl">120</span><span class="op">)</span>, longitudelim <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="op">-</span><span class="fl">130</span>, <span class="op">-</span><span class="fl">50</span><span class="op">)</span>,</span></span>
<span class="r-in"><span>    col <span class="op">=</span> <span class="st">"lightgray"</span>, projection <span class="op">=</span> <span class="st">"+proj=stere +lat_0=90"</span></span></span>
<span class="r-in"><span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="fu">mapScalebar</span><span class="op">(</span><span class="op">)</span></span></span>
<span class="r-plt img"><img src="mapScalebar-1.png" alt="" width="700" height="700"></span>
<span class="r-in"><span><span class="co"># }</span></span></span>
<span class="r-in"><span></span></span>
</code></pre></div>
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