does this through special markup rules for inserting and formatting data values inside a string. Figure <a href="controlling-tooltips.html#fig:hovertemplate">25.5</a> provides an example of inserting <code>x</code> and <code>y</code> in the tooltip through the special <code>%{variable:format}</code> markup as well as customization of the secondary box through <code>&lt;extra&gt;</code> tag. For a full description of this attribute, including the formatting rules, see <a href="https://plot.ly/r/reference/#sc