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<div class="section" id="compute-slice-command">
<span id="index-0"></span><h1>compute slice command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="n">ID</span> <span class="n">group</span><span class="o">-</span><span class="n">ID</span> <span class="nb">slice</span> <span class="n">Nstart</span> <span class="n">Nstop</span> <span class="n">Nskip</span> <span class="n">input1</span> <span class="n">input2</span> <span class="o">...</span>
</pre></div>
</div>
<ul class="simple">
<li>ID, group-ID are documented in <a class="reference internal" href="compute.html"><span class="doc">compute</span></a> command</li>
<li>slice = style name of this compute command</li>
<li>Nstart = starting index within input vector(s)</li>
<li>Nstop = stopping index within input vector(s)</li>
<li>Nskip = extract every Nskip elements from input vector(s)</li>
<li>input = c_ID, c_ID[N], f_ID, f_ID[N]</li>
</ul>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">c_ID</span> <span class="o">=</span> <span class="k">global</span> <span class="n">vector</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">a</span> <span class="n">compute</span> <span class="k">with</span> <span class="n">ID</span>
<span class="n">c_ID</span><span class="p">[</span><span class="n">I</span><span class="p">]</span> <span class="o">=</span> <span class="n">Ith</span> <span class="n">column</span> <span class="n">of</span> <span class="k">global</span> <span class="n">array</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">a</span> <span class="n">compute</span> <span class="k">with</span> <span class="n">ID</span>
<span class="n">f_ID</span> <span class="o">=</span> <span class="k">global</span> <span class="n">vector</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">a</span> <span class="n">fix</span> <span class="k">with</span> <span class="n">ID</span>
<span class="n">f_ID</span><span class="p">[</span><span class="n">I</span><span class="p">]</span> <span class="o">=</span> <span class="n">Ith</span> <span class="n">column</span> <span class="n">of</span> <span class="k">global</span> <span class="n">array</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">a</span> <span class="n">fix</span> <span class="k">with</span> <span class="n">ID</span>
<span class="n">v_name</span> <span class="o">=</span> <span class="n">vector</span> <span class="n">calculated</span> <span class="n">by</span> <span class="n">an</span> <span class="n">vector</span><span class="o">-</span><span class="n">style</span> <span class="n">variable</span> <span class="k">with</span> <span class="n">name</span>
</pre></div>
</div>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="mi">1</span> <span class="nb">all</span> <span class="nb">slice</span> <span class="mi">1</span> <span class="mi">100</span> <span class="mi">10</span> <span class="n">c_msdmol</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span>
<span class="n">compute</span> <span class="mi">1</span> <span class="nb">all</span> <span class="nb">slice</span> <span class="mi">301</span> <span class="mi">400</span> <span class="mi">1</span> <span class="n">c_msdmol</span><span class="p">[</span><span class="mi">4</span><span class="p">]</span> <span class="n">v_myVec</span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Define a calculation that &#8220;slices&#8221; one or more vector inputs into
smaller vectors, one per listed input. The inputs can be global
quantities; they cannot be per-atom or local quantities.
<a class="reference internal" href="compute.html"><span class="doc">Computes</span></a> and <a class="reference internal" href="fix.html"><span class="doc">fixes</span></a> and vector-style
<a class="reference internal" href="variable.html"><span class="doc">variables</span></a> can generate such global quantities. The
group specified with this command is ignored.</p>
<p>The values extracted from the input vector(s) are determined by the
<em>Nstart</em>, <em>Nstop</em>, and <em>Nskip</em> parameters. The elements of an input
vector of length N are indexed from 1 to N. Starting at element
<em>Nstart</em>, every Mth element is extracted, where M = <em>Nskip</em>, until
element <em>Nstop</em> is reached. The extracted quantities are stored as a
vector, which is typically shorter than the input vector.</p>
<p>Each listed input is operated on independently to produce one output
vector. Each listed input must be a global vector or column of a
global array calculated by another <a class="reference internal" href="compute.html"><span class="doc">compute</span></a> or
<a class="reference internal" href="fix.html"><span class="doc">fix</span></a>.</p>
<p>If an input value begins with &#8220;<a href="#id1"><span class="problematic" id="id2">c_</span></a>&#8221;, a compute ID must follow which has
been previously defined in the input script and which generates a
global vector or array. See the individual <a class="reference internal" href="compute.html"><span class="doc">compute</span></a> doc
page for details. If no bracketed integer is appended, the vector
calculated by the compute is used. If a bracketed integer is
appended, the Ith column of the array calculated by the compute is
used. Users can also write code for their own compute styles and <a class="reference internal" href="Section_modify.html"><span class="doc">add them to LAMMPS</span></a>.</p>
<p>If a value begins with &#8220;<a href="#id3"><span class="problematic" id="id4">f_</span></a>&#8221;, a fix ID must follow which has been
previously defined in the input script and which generates a global
vector or array. See the individual <a class="reference internal" href="fix.html"><span class="doc">fix</span></a> doc page for
details. Note that some fixes only produce their values on certain
timesteps, which must be compatible with when compute slice references
the values, else an error results. If no bracketed integer is
appended, the vector calculated by the fix is used. If a bracketed
integer is appended, the Ith column of the array calculated by the fix
is used. Users can also write code for their own fix style and <a class="reference internal" href="Section_modify.html"><span class="doc">add them to LAMMPS</span></a>.</p>
<p>If an input value begins with &#8220;<a href="#id5"><span class="problematic" id="id6">v_</span></a>&#8221;, a variable name must follow which
has been previously defined in the input script. Only vector-style
variables can be referenced. See the <a class="reference internal" href="variable.html"><span class="doc">variable</span></a> command
for details. Note that variables of style <em>vector</em> define a formula
which can reference individual atom properties or thermodynamic
keywords, or they can invoke other computes, fixes, or variables when
they are evaluated, so this is a very general means of specifying
quantities to slice.</p>
<p>If a single input is specified this compute produces a global vector,
even if the length of the vector is 1. If multiple inputs are
specified, then a global array of values is produced, with the number
of columns equal to the number of inputs specified.</p>
<hr class="docutils" />
<p><strong>Output info:</strong></p>
<p>This compute calculates a global vector if a single input value is
specified or a global array with N columns where N is the number of
inputs. The length of the vector or the number of rows in the array
is equal to the number of values extracted from each input vector.
These values can be used by any command that uses global vector or
array values from a compute as input. See <a class="reference internal" href="Section_howto.html#howto-15"><span class="std std-ref">this section</span></a> for an overview of LAMMPS output
options.</p>
<p>The vector or array values calculated by this compute are simply
copies of values generated by computes or fixes or variables that are
input vectors to this compute. If there is a single input vector of
intensive and/or extensive values, then each value in the vector of
values calculated by this compute will be &#8220;intensive&#8221; or &#8220;extensive&#8221;,
depending on the corresponding input value. If there are multiple
input vectors, and all the values in them are intensive, then the
array values calculated by this compute are &#8220;intensive&#8221;. If there are
multiple input vectors, and any value in them is extensive, then the
array values calculated by this compute are &#8220;extensive&#8221;. Values
produced by a variable are treated as intensive.</p>
<p>The vector or array values will be in whatever <span class="xref doc">units</span> the
input quantities are in.</p>
</div>
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<blockquote>
<div>none</div></blockquote>
</div>
<div class="section" id="related-commands">
<h2>Related commands</h2>
<p><a class="reference internal" href="compute.html"><span class="doc">compute</span></a>, <a class="reference internal" href="fix.html"><span class="doc">fix</span></a>, <a class="reference internal" href="compute_reduce.html"><span class="doc">compute reduce</span></a></p>
<p><strong>Default:</strong> none</p>
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