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compose_data() by prefixing a character vector to the original
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  <div class="col-md-9 contents">
    <div class="page-header">
    <h1>Prefix function generator for composing dimension index columns</h1>
    <small class="dont-index">Source: <a href="https://github.com/mjskay/tidybayes/blob/HEAD/R/compose_data.R" class="external-link"><code>R/compose_data.R</code></a></small>
    <div class="hidden name"><code>n_prefix.Rd</code></div>
    </div>

    <div class="ref-description">
    <p>Generates a function for generating names of index columns for factors in
<code><a href="compose_data.html">compose_data()</a></code> by prefixing a character vector to the original
column name.</p>
    </div>

    <div id="ref-usage">
    <div class="sourceCode"><pre class="sourceCode r"><code><span><span class="fu">n_prefix</span><span class="op">(</span><span class="va">prefix</span><span class="op">)</span></span></code></pre></div>
    </div>

    <div id="arguments">
    <h2>Arguments</h2>


<dl><dt id="arg-prefix">prefix<a class="anchor" aria-label="anchor" href="#arg-prefix"></a></dt>
<dd><p>Character vector to be prepended to column names by
<code><a href="compose_data.html">compose_data()</a></code> to create index columns. Typically something
like <code>"n"</code> (that is the default used in the <code>.n_name</code> argument
of <code><a href="compose_data.html">compose_data()</a></code>).</p>
<p>Returns a function. The function returned takes a character vector, <code>name</code>
and returns <code>paste0(prefix, "_", name)</code>, unless <code>name</code> is empty, in
which case it will return <code>prefix</code>.</p>
<p><code>n_prefix("n")</code> is the default method that <code><a href="compose_data.html">compose_data()</a></code> uses to
generate column names for variables storing the number of levels in a factor. Under
this method, given a data frame
<code>df</code> with a factor column <code>"foo"</code> containing 5 levels, the results of
<code>compose_data(df)</code> will include an element named <code>"n"</code> (the result of
<code>n_prefix("n")("")</code>) equal to the number of rows in <code>df</code> and an element
named <code>"n_foo"</code> (the result of <code>n_prefix("n")("foo")</code>) equal to the
number of levels in <code>df$foo</code>.</p></dd>

</dl></div>
    <div id="see-also">
    <h2>See also</h2>
    <div class="dont-index"><p>The <code>.n_name</code> argument of <code><a href="compose_data.html">compose_data()</a></code>.</p></div>
    </div>

    <div id="ref-examples">
    <h2>Examples</h2>
    <div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><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://magrittr.tidyverse.org" class="external-link">magrittr</a></span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="va">df</span> <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/data.frame.html" class="external-link">data.frame</a></span><span class="op">(</span></span></span>
<span class="r-in"><span>  plot <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/factor.html" class="external-link">factor</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/paste.html" class="external-link">paste0</a></span><span class="op">(</span><span class="st">"p"</span>, <span class="fu"><a href="https://rdrr.io/r/base/rep.html" class="external-link">rep</a></span><span class="op">(</span><span class="fl">1</span><span class="op">:</span><span class="fl">8</span>, times <span class="op">=</span> <span class="fl">2</span><span class="op">)</span><span class="op">)</span><span class="op">)</span>,</span></span>
<span class="r-in"><span>  site <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/factor.html" class="external-link">factor</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/paste.html" class="external-link">paste0</a></span><span class="op">(</span><span class="st">"s"</span>, <span class="fu"><a href="https://rdrr.io/r/base/rep.html" class="external-link">rep</a></span><span class="op">(</span><span class="fl">1</span><span class="op">:</span><span class="fl">4</span>, each <span class="op">=</span> <span class="fl">2</span>, times <span class="op">=</span> <span class="fl">2</span><span class="op">)</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="op">)</span></span></span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="co"># without changing `.n_name`, compose_data() will prefix indices</span></span></span>
<span class="r-in"><span><span class="co"># with "n" by default</span></span></span>
<span class="r-in"><span><span class="va">df</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html" class="external-link">%&gt;%</a></span></span></span>
<span class="r-in"><span>  <span class="fu"><a href="compose_data.html">compose_data</a></span><span class="op">(</span><span class="op">)</span></span></span>
<span class="r-out co"><span class="r-pr">#&gt;</span> $plot</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  [1] 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> $n_plot</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> [1] 8</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> $site</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  [1] 1 1 2 2 3 3 4 4 1 1 2 2 3 3 4 4</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> $n_site</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> [1] 4</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> $n</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> [1] 16</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> </span>
<span class="r-in"><span></span></span>
<span class="r-in"><span><span class="co"># you can use n_prefix() to define a different prefix (e.g. "N"):</span></span></span>
<span class="r-in"><span><span class="va">df</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pipe.html" class="external-link">%&gt;%</a></span></span></span>
<span class="r-in"><span>  <span class="fu"><a href="compose_data.html">compose_data</a></span><span class="op">(</span>.n_name <span class="op">=</span> <span class="fu">n_prefix</span><span class="op">(</span><span class="st">"N"</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-out co"><span class="r-pr">#&gt;</span> $plot</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  [1] 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> $N_plot</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> [1] 8</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> $site</span>
<span class="r-out co"><span class="r-pr">#&gt;</span>  [1] 1 1 2 2 3 3 4 4 1 1 2 2 3 3 4 4</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> $N_site</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> [1] 4</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> </span>
<span class="r-out co"><span class="r-pr">#&gt;</span> $N</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> [1] 16</span>
<span class="r-out co"><span class="r-pr">#&gt;</span> </span>
<span class="r-in"><span></span></span>
</code></pre></div>
    </div>
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