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scheme (see References 1 to 4).  A few such schemes are built-in, and may be referred to
by name ("gmt_gebco", "gmt_globe", "gmt_ocean", or "gmt_relief")
while others are handled by reading local files that are in GMT
format, or URLs providing such files (see Reference 3).'><meta property="og:description" content='colormapGMT creates colormaps in the Generic Mapping Tools (GMT)
scheme (see References 1 to 4).  A few such schemes are built-in, and may be referred to
by name ("gmt_gebco", "gmt_globe", "gmt_ocean", or "gmt_relief")
while others are handled by reading local files that are in GMT
format, or URLs providing such files (see Reference 3).'></head><body>
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      <h1>Create a GMT-type (CPT) Colormap</h1>
      <small class="dont-index">Source: <a href="https://github.com/dankelley/oce/blob/HEAD/R/colors.R" class="external-link"><code>R/colors.R</code></a></small>
      <div class="d-none name"><code>colormapGMT.Rd</code></div>
    </div>

    <div class="ref-description section level2">
    <p><code>colormapGMT</code> creates colormaps in the Generic Mapping Tools (GMT)
scheme (see References 1 to 4).  A few such schemes are built-in, and may be referred to
by name (<code>"gmt_gebco"</code>, <code>"gmt_globe"</code>, <code>"gmt_ocean"</code>, or <code>"gmt_relief"</code>)
while others are handled by reading local files that are in GMT
format, or URLs providing such files (see Reference 3).</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">colormapGMT</span><span class="op">(</span><span class="va">name</span>, debug <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/options.html" class="external-link">getOption</a></span><span class="op">(</span><span class="st">"oceDebug"</span><span class="op">)</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-name">name<a class="anchor" aria-label="anchor" href="#arg-name"></a></dt>
<dd><p>character value specifying the GMT scheme, or a source for such
a scheme. Four pre-defined schemes are available, accessed by setting <code>name</code> to
<code>"gmt_gebco"</code>, <code>"gmt_globe"</code>, <code>"gmt_ocean"</code>, or <code>"gmt_relief"</code>. If <code>name</code> is
not one of these values, then it is taken to be the name of a local file
in GMT format or, if no such file is found, a URL holding such a file.</p></dd>


<dt id="arg-debug">debug<a class="anchor" aria-label="anchor" href="#arg-debug"></a></dt>
<dd><p>integer that, if positive, indicates to print some debugging output</p></dd>

</dl></div>
    <div class="section level2">
    <h2 id="value">Value<a class="anchor" aria-label="anchor" href="#value"></a></h2>
    <p><code>colormap</code> returns a list, in the same format as the return value for <code><a href="colormap.html">colormap()</a></code>.</p>
    </div>
    <div class="section level2">
    <h2 id="details">Details<a class="anchor" aria-label="anchor" href="#details"></a></h2>
    <p>The GMT files understood by colormapGMT are what GMT calls
"Regular CPT files" (see reference 4).  This is a text format that
can be read and (with care) edited in a text editor.  There
are three categories of lines within this file.  (1) Any
line starting with the <code>"#"</code> character is a comment, and is ignored
by colormapGMT. (2) Lines with 8 numbers specify colour bands.
The first number is a z value, and the three numbers after that
are red, green and blue values in the range from 0 to 255. This
set of 4 numbers is followed on the same line with similar values.
Think of this sequence as describing a band of colours between
two z values. (3) Lines starting with a character, followed
by three numbers, specify particular codings.  The character <code>"B"</code>
specifies background colour, while <code>"F"</code> specifies foreground
colour, and <code>"N"</code> specifies the colour to be used for missing
data (the letter stands for not-a-number).  Only <code>"N"</code> is used
by colormapGMT, and it takes on the role that the <code>missingColor</code>
argument would otherwise have.  (This is why <code>missingColor</code> is not
permitted if <code>name</code> is given.)</p>
    </div>
    <div class="section level2">
    <h2 id="references">References<a class="anchor" aria-label="anchor" href="#references"></a></h2>

<ol><li><p>General overview of GMT system
<code>https://www.generic-mapping-tools.org</code>.</p></li>
<li><p>Information on GMT color schemes
<code>https://docs.generic-mapping-tools.org/dev/cookbook/cpts.html</code></p></li>
<li><p>Source of GMT specification files
<code>https://beamreach.org/maps/gmt/share/cpt/</code></p></li>
<li><p>CPT (color palette table) format
<code>https://www.soest.hawaii.edu/gmt/gmt/html/GMT_Docs.html#x1-820004.15</code></p></li>
</ol></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>Other things related to colors:
<code><a href="colormap.html">colormap</a>()</code>,
<code><a href="oceColors9B.html">oceColors9B</a>()</code>,
<code><a href="oceColorsCDOM.html">oceColorsCDOM</a>()</code>,
<code><a href="oceColorsChlorophyll.html">oceColorsChlorophyll</a>()</code>,
<code><a href="oceColorsClosure.html">oceColorsClosure</a>()</code>,
<code><a href="oceColorsDensity.html">oceColorsDensity</a>()</code>,
<code><a href="oceColorsFreesurface.html">oceColorsFreesurface</a>()</code>,
<code><a href="oceColorsGebco.html">oceColorsGebco</a>()</code>,
<code><a href="oceColorsJet.html">oceColorsJet</a>()</code>,
<code><a href="oceColorsOxygen.html">oceColorsOxygen</a>()</code>,
<code><a href="oceColorsPAR.html">oceColorsPAR</a>()</code>,
<code><a href="oceColorsPalette.html">oceColorsPalette</a>()</code>,
<code><a href="oceColorsPhase.html">oceColorsPhase</a>()</code>,
<code><a href="oceColorsSalinity.html">oceColorsSalinity</a>()</code>,
<code><a href="oceColorsTemperature.html">oceColorsTemperature</a>()</code>,
<code><a href="oceColorsTurbidity.html">oceColorsTurbidity</a>()</code>,
<code><a href="oceColorsTurbo.html">oceColorsTurbo</a>()</code>,
<code><a href="oceColorsTwo.html">oceColorsTwo</a>()</code>,
<code><a href="oceColorsVelocity.html">oceColorsVelocity</a>()</code>,
<code><a href="oceColorsViridis.html">oceColorsViridis</a>()</code>,
<code><a href="oceColorsVorticity.html">oceColorsVorticity</a>()</code>,
<code><a href="ocecolors.html">ocecolors</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>

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