>
      <div class="d-none name"><code>chapter4_AccMetrics.Rmd</code></div>
    </div>

    
    
<div class="section level2">
<h2 id="why-do-we-need-to-extract-metrics">Why do we need to extract metrics<a class="anchor" aria-label="anchor" href="#why-do-we-need-to-extract-metrics"></a>
</h2>
<p>Wearable accelerometers are widely used in health research to study
physical activity, sleep, and other behaviours. Most modern
accelerometers can collect and store at least 30 values per second
expressed in units o