vement. Due to the increasing ease with which GPS-data can be collected via modern smartphones, recent years have witnessed a marked increase in the use of GPS-based activity measures in the study of mental health.</p>
<p>Figure <a href="activity.html#fig:fourweekgps">6.5</a> shows GPS-data of two people, collected over a period of four weeks, via the Google timeline smartphone app. Data can be found in the <code>emaph</code> package (see <code>?locations</code>).</p>
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