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<li>N-dimensional datasets (<tt class="docutils literal"><span class="pre">astropy.nddata</span></tt>)</li>
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<div class="section" id="n-dimensional-datasets-astropy-nddata">
<span id="astropy-nddata"></span><h1>N-dimensional datasets (<a class="reference internal" href="#module-astropy.nddata" title="astropy.nddata"><tt class="xref py py-obj docutils literal"><span class="pre">astropy.nddata</span></tt></a>)<a class="headerlink" href="#n-dimensional-datasets-astropy-nddata" title="Permalink to this headline">¶</a></h1>
<div class="section" id="introduction">
<h2>Introduction<a class="headerlink" href="#introduction" title="Permalink to this headline">¶</a></h2>
<p><a class="reference internal" href="#module-astropy.nddata" title="astropy.nddata"><tt class="xref py py-obj docutils literal"><span class="pre">astropy.nddata</span></tt></a> provides the <a class="reference internal" href="../_generated/astropy.nddata.nddata.NDData.html#astropy.nddata.nddata.NDData" title="astropy.nddata.nddata.NDData"><tt class="xref py py-obj docutils literal"><span class="pre">NDData</span></tt></a>
class and related tools to manage n-dimensional array-based data (e.g.
CCD images, IFU data, grid-based simulation data, ...). This is more than
just <tt class="xref py py-obj docutils literal"><span class="pre">numpy.ndarray</span></tt> objects, because it provides metadata that cannot
be easily provided by a single array.</p>
<p>This subpackage also provides new convolution routines that differ from
Scipy in that they offer a proper treatment of NaN values.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The <a class="reference internal" href="../_generated/astropy.nddata.nddata.NDData.html#astropy.nddata.nddata.NDData" title="astropy.nddata.nddata.NDData"><tt class="xref py py-obj docutils literal"><span class="pre">NDData</span></tt></a> class is still under
development, and support for WCS and units is not yet implemented.</p>
</div>
</div>
<div class="section" id="getting-started">
<h2>Getting started<a class="headerlink" href="#getting-started" title="Permalink to this headline">¶</a></h2>
<p>An <a class="reference internal" href="../_generated/astropy.nddata.nddata.NDData.html#astropy.nddata.nddata.NDData" title="astropy.nddata.nddata.NDData"><tt class="xref py py-obj docutils literal"><span class="pre">NDData</span></tt></a> object can be instantiated by passing it an
n-dimensional Numpy array:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">astropy.nddata</span> <span class="kn">import</span> <span class="n">NDData</span>
<span class="gp">>>> </span><span class="n">array</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">random</span><span class="o">.</span><span class="n">random</span><span class="p">((</span><span class="mi">12</span><span class="p">,</span> <span class="mi">12</span><span class="p">,</span> <span class="mi">12</span><span class="p">))</span> <span class="c"># a random 3-dimensional array</span>
<span class="gp">>>> </span><span class="n">ndd</span> <span class="o">=</span> <span class="n">NDData</span><span class="p">(</span><span class="n">array</span><span class="p">)</span>
</pre></div>
</div>
<p>This object has a few attributes in common with Numpy:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">ndd</span><span class="o">.</span><span class="n">ndim</span>
<span class="go">3</span>
<span class="gp">>>> </span><span class="n">ndd</span><span class="o">.</span><span class="n">shape</span>
<span class="go">(12, 12, 12)</span>
<span class="gp">>>> </span><span class="n">ndd</span><span class="o">.</span><span class="n">dtype</span>
<span class="go">dtype('float64')</span>
</pre></div>
</div>
<p>The underlying Numpy array can be accessed via the <tt class="xref py py-obj docutils literal"><span class="pre">data</span></tt> attribute:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">ndd</span><span class="o">.</span><span class="n">data</span>
<span class="go">array([[[ 0.05621944, 0.85569765, 0.71609697, ..., 0.76049288,</span>
<span class="gp">...</span>
</pre></div>
</div>
<p>Values can be masked using the <tt class="xref py py-obj docutils literal"><span class="pre">mask</span></tt> attribute, which should be a boolean
Numpy array with the same dimensions as the data, e.g.:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">ndd</span><span class="o">.</span><span class="n">mask</span> <span class="o">=</span> <span class="n">ndd</span><span class="o">.</span><span class="n">data</span> <span class="o">></span> <span class="mf">0.9</span>
</pre></div>
</div>
<p>A mask value of <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt> indicates a value that should be ignored, while a mask
value of <tt class="xref py py-obj docutils literal"><span class="pre">False</span></tt> indicates a valid value.</p>
<p>Similarly, attributes are available to store generic meta-data, flags, and
uncertainties, and the <a class="reference internal" href="../_generated/astropy.nddata.nddata.NDData.html#astropy.nddata.nddata.NDData" title="astropy.nddata.nddata.NDData"><tt class="xref py py-obj docutils literal"><span class="pre">NDData</span></tt></a> class includes methods to
combine datasets with arithmetic operations (which include uncertainties propagation).
These are described in <a class="reference internal" href="nddata.html"><em>NDData overview</em></a>.</p>
</div>
<div class="section" id="using-nddata">
<h2>Using <tt class="xref py py-obj docutils literal"><span class="pre">nddata</span></tt><a class="headerlink" href="#using-nddata" title="Permalink to this headline">¶</a></h2>
<div class="toctree-wrapper compound">
<ul>
<li class="toctree-l1"><a class="reference internal" href="nddata.html">NDData overview</a><ul>
<li class="toctree-l2"><a class="reference internal" href="nddata.html#initializing">Initializing</a></li>
<li class="toctree-l2"><a class="reference internal" href="nddata.html#mask">Mask</a></li>
<li class="toctree-l2"><a class="reference internal" href="nddata.html#flags">Flags</a></li>
<li class="toctree-l2"><a class="reference internal" href="nddata.html#uncertainties">Uncertainties</a></li>
<li class="toctree-l2"><a class="reference internal" href="nddata.html#arithmetic">Arithmetic</a></li>
<li class="toctree-l2"><a class="reference internal" href="nddata.html#meta-data">Meta-data</a></li>
<li class="toctree-l2"><a class="reference internal" href="nddata.html#converting-to-numpy-arrays">Converting to Numpy arrays</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="convolution.html">Convolution</a><ul>
<li class="toctree-l2"><a class="reference internal" href="convolution.html#introduction">Introduction</a></li>
<li class="toctree-l2"><a class="reference internal" href="convolution.html#usage">Usage</a></li>
<li class="toctree-l2"><a class="reference internal" href="convolution.html#examples">Examples</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="subclassing.html">Subclassing <tt class="docutils literal"><span class="pre">NDData</span></tt> and <tt class="docutils literal"><span class="pre">NDUncertainty</span></tt></a><ul>
<li class="toctree-l2"><a class="reference internal" href="subclassing.html#subclassing-nduncertainty">Subclassing <tt class="docutils literal"><span class="pre">NDUncertainty</span></tt></a></li>
</ul>
</li>
</ul>
</div>
</div>
<div class="section" id="reference-api">
<h2>Reference/API<a class="headerlink" href="#reference-api" title="Permalink to this headline">¶</a></h2>
<div class="section" id="module-astropy.nddata">
<span id="astropy-nddata-module"></span><h3>astropy.nddata Module<a class="headerlink" href="#module-astropy.nddata" title="Permalink to this headline">¶</a></h3>
<p>The <tt class="xref py py-obj docutils literal"><span class="pre">nddata</span></tt> subpackage provides the <a class="reference internal" href="../_generated/astropy.nddata.nddata.NDData.html#astropy.nddata.nddata.NDData" title="astropy.nddata.nddata.NDData"><tt class="xref py py-obj docutils literal"><span class="pre">NDData</span></tt></a>
class and related tools to manage n-dimensional array-based data (e.g.
CCD images, IFU Data, grid-based simulation data, ...). This is more than
just <tt class="xref py py-obj docutils literal"><span class="pre">numpy.ndarray</span></tt> objects, because it provides metadata that cannot
be easily provided by a single array.</p>
<div class="section" id="functions">
<h4>Functions<a class="headerlink" href="#functions" title="Permalink to this headline">¶</a></h4>
<table border="1" class="longtable docutils">
<colgroup>
<col width="10%" />
<col width="90%" />
</colgroup>
<tbody valign="top">
<tr class="row-odd"><td><a class="reference internal" href="../_generated/astropy.nddata.convolution.convolve.convolve.html#astropy.nddata.convolution.convolve.convolve" title="astropy.nddata.convolution.convolve.convolve"><tt class="xref py py-obj docutils literal"><span class="pre">convolve</span></tt></a>(array, kernel[, boundary, ...])</td>
<td>Convolve an array with a kernel.</td>
</tr>
<tr class="row-even"><td><a class="reference internal" href="../_generated/astropy.nddata.convolution.convolve.convolve_fft.html#astropy.nddata.convolution.convolve.convolve_fft" title="astropy.nddata.convolution.convolve.convolve_fft"><tt class="xref py py-obj docutils literal"><span class="pre">convolve_fft</span></tt></a>(array, kernel[, boundary, ...])</td>
<td>Convolve an ndarray with an nd-kernel.</td>
</tr>
<tr class="row-odd"><td><a class="reference internal" href="../_generated/astropy.nddata.convolution.make_kernel.make_kernel.html#astropy.nddata.convolution.make_kernel.make_kernel" title="astropy.nddata.convolution.make_kernel.make_kernel"><tt class="xref py py-obj docutils literal"><span class="pre">make_kernel</span></tt></a>(kernelshape[, kernelwidth, ...])</td>
<td>Create a smoothing kernel for use with <tt class="xref py py-obj docutils literal"><span class="pre">convolve</span></tt> or <tt class="xref py py-obj docutils literal"><span class="pre">convolve_fft</span></tt>.</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="classes">
<h4>Classes<a class="headerlink" href="#classes" title="Permalink to this headline">¶</a></h4>
<table border="1" class="longtable docutils">
<colgroup>
<col width="10%" />
<col width="90%" />
</colgroup>
<tbody valign="top">
<tr class="row-odd"><td><a class="reference internal" href="../_generated/astropy.nddata.flag_collection.FlagCollection.html#astropy.nddata.flag_collection.FlagCollection" title="astropy.nddata.flag_collection.FlagCollection"><tt class="xref py py-obj docutils literal"><span class="pre">FlagCollection</span></tt></a>(*args, **kwargs)</td>
<td>The purpose of this class is to provide a dictionary for containing arrays of flags for the <tt class="xref py py-obj docutils literal"><span class="pre">NDData</span></tt> class.</td>
</tr>
<tr class="row-even"><td><a class="reference internal" href="../_generated/astropy.nddata.nduncertainty.IncompatibleUncertaintiesException.html#astropy.nddata.nduncertainty.IncompatibleUncertaintiesException" title="astropy.nddata.nduncertainty.IncompatibleUncertaintiesException"><tt class="xref py py-obj docutils literal"><span class="pre">IncompatibleUncertaintiesException</span></tt></a></td>
<td>This exception should be used to indicate cases in which uncertainties with two different classes can not be propagated.</td>
</tr>
<tr class="row-odd"><td><a class="reference internal" href="../_generated/astropy.nddata.nduncertainty.MissingDataAssociationException.html#astropy.nddata.nduncertainty.MissingDataAssociationException" title="astropy.nddata.nduncertainty.MissingDataAssociationException"><tt class="xref py py-obj docutils literal"><span class="pre">MissingDataAssociationException</span></tt></a></td>
<td>This exception should be used to indicate that an uncertainty instance has not been associated with a parent <a class="reference internal" href="../_generated/astropy.nddata.nddata.NDData.html#astropy.nddata.nddata.NDData" title="astropy.nddata.nddata.NDData"><tt class="xref py py-obj docutils literal"><span class="pre">NDData</span></tt></a> object.</td>
</tr>
<tr class="row-even"><td><a class="reference internal" href="../_generated/astropy.nddata.nddata.NDData.html#astropy.nddata.nddata.NDData" title="astropy.nddata.nddata.NDData"><tt class="xref py py-obj docutils literal"><span class="pre">NDData</span></tt></a>(data[, uncertainty, mask, flags, ...])</td>
<td>A Superclass for array-based data in Astropy.</td>
</tr>
<tr class="row-odd"><td><a class="reference internal" href="../_generated/astropy.nddata.nduncertainty.NDUncertainty.html#astropy.nddata.nduncertainty.NDUncertainty" title="astropy.nddata.nduncertainty.NDUncertainty"><tt class="xref py py-obj docutils literal"><span class="pre">NDUncertainty</span></tt></a></td>
<td>This is the base class for uncertainty classes used with NDData.</td>
</tr>
<tr class="row-even"><td><a class="reference internal" href="../_generated/astropy.nddata.nduncertainty.StdDevUncertainty.html#astropy.nddata.nduncertainty.StdDevUncertainty" title="astropy.nddata.nduncertainty.StdDevUncertainty"><tt class="xref py py-obj docutils literal"><span class="pre">StdDevUncertainty</span></tt></a>([array, copy])</td>
<td>A class for standard deviation uncertaintys</td>
</tr>
</tbody>
</table>
</div>
</div>
</div>
</div>
</div>
</div>
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<ul>
<li><a class="reference internal" href="#">N-dimensional datasets (<tt class="docutils literal"><span class="pre">astropy.nddata</span></tt>)</a><ul>
<li><a class="reference internal" href="#introduction">Introduction</a></li>
<li><a class="reference internal" href="#getting-started">Getting started</a></li>
<li><a class="reference internal" href="#using-nddata">Using <tt class="docutils literal"><span class="pre">nddata</span></tt></a><ul>
</ul>
</li>
<li><a class="reference internal" href="#reference-api">Reference/API</a><ul>
<li><a class="reference internal" href="#module-astropy.nddata">astropy.nddata Module</a><ul>
<li><a class="reference internal" href="#functions">Functions</a><ul>
</ul>
</li>
<li><a class="reference internal" href="#classes">Classes</a><ul>
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