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  <section id="t-digest-functions">
<h1 id="functions-tdigest--page-root">T-Digest functions<a class="headerlink" href="#functions-tdigest--page-root" title="Permalink to this heading">#</a></h1>
<section id="data-structures">
<h2 id="data-structures">Data structures<a class="headerlink" href="#data-structures" title="Permalink to this heading">#</a></h2>
<p>A T-digest is a data sketch which stores approximate percentile
information.  The Trino type for this data structure is called <code class="docutils literal notranslate"><span class="pre">tdigest</span></code>.
T-digests can be merged, and for storage and retrieval they can be cast
to and from <code class="docutils literal notranslate"><span class="pre">VARBINARY</span></code>.</p>
</section>
<section id="functions">
<h2 id="functions">Functions<a class="headerlink" href="#functions" title="Permalink to this heading">#</a></h2>
<dl class="py function">
<dt class="sig sig-object py">
<span class="sig-name descname"><span class="pre">merge</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">tdigest</span></span></em><span class="sig-paren">)</span> <span class="sig-return"><span class="sig-return-icon">→</span> <span class="sig-return-typehint"><span class="pre">tdigest</span></span></span></dt>
<dd><p>Aggregates all inputs into a single <code class="docutils literal notranslate"><span class="pre">tdigest</span></code>.</p>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py">
<span class="sig-name descname"><span class="pre">value_at_quantile</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">tdigest</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">quantile</span></span></em><span class="sig-paren">)</span> <span class="sig-return"><span class="sig-return-icon">→</span> <span class="sig-return-typehint"><span class="pre">double</span></span></span></dt>
<dd><p>Returns the approximate percentile value from the T-digest, given
the number <code class="docutils literal notranslate"><span class="pre">quantile</span></code> between 0 and 1.</p>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py">
<span class="sig-name descname"><span class="pre">values_at_quantiles</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">tdigest</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">quantiles</span></span></em><span class="sig-paren">)</span></dt>
<dd><p>Returns the approximate percentile values as an array, given the input
T-digest and an array of values between 0 and 1, which
represent the quantiles to return.</p>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py" id="tdigest_agg">
<span class="sig-name descname"><span class="pre">tdigest_agg</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">x</span></span></em><span class="sig-paren">)</span> <span class="sig-return"><span class="sig-return-icon">→</span> <span class="sig-return-typehint"><span class="pre">tdigest</span></span></span><a class="headerlink" href="#tdigest_agg" title="Permalink to this definition">#</a></dt>
<dd><p>Composes all input values of <code class="docutils literal notranslate"><span class="pre">x</span></code> into a <code class="docutils literal notranslate"><span class="pre">tdigest</span></code>. <code class="docutils literal notranslate"><span class="pre">x</span></code> can be
of any numeric type.</p>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py">
<span class="sig-name descname"><span class="pre">tdigest_agg</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">x</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">w</span></span></em><span class="sig-paren">)</span> <span class="sig-return"><span class="sig-return-icon">→</span> <span class="sig-return-typehint"><span class="pre">tdigest</span></span></span></dt>
<dd><p>Composes all input values of <code class="docutils literal notranslate"><span class="pre">x</span></code> into a <code class="docutils literal notranslate"><span class="pre">tdigest</span></code> using
the per-item weight <code class="docutils literal notranslate"><span class="pre">w</span></code>. <code class="docutils literal notranslate"><span class="pre">w</span></code> must be greater or equal than 1.
<code class="docutils literal notranslate"><span class="pre">x</span></code> and <code class="docutils literal notranslate"><span class="pre">w</span></code> can be of any numeric type.</p>
</dd></dl>
</section>
</section>


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