s <code>dtrackr</code> uses
formulae to specify the inclusion and exclusion criteria, to construct
an appropriate formulae for <code>dtrackr</code> using values that are
parametrised from a helper function requires injection support, using
<code><a href="https://rlang.r-lib.org/reference/inject.html" class="external-link">rlang::inject()</a></code>. This is an advanced R topic but the
following example gives a sense of what is possible.</p>
<div class="sourceCode" id="cb10"><pre class="downlit sourceCode r"