span class='co'># using tf$cond directly:</span>
<span class='va'>raw</span> <span class='op'>&lt;-</span> <span class='kw'>function</span><span class='op'>(</span><span class='va'>x</span><span class='op'>)</span> <span class='va'>tf</span><span class='op'>$</span><span class='fu'>cond</span><span class='op'>(</span><span class='va'>x</span> <span class='op'>&gt;</span> <span class='fl'>0</span>, <span class='kw'>function</span><span class='op'>(</span><span class='op'>)</span> <span class='va'>x</span> <s