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Updated documentation for Duration.

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nikunjgoel95 2021-01-25 17:04:02 -05:00
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docs/features/phone-locations.md
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@ -121,7 +121,7 @@ Features description for `[PHONE_LOCATIONS][PROVIDERS][DORYAB]`:
|averagespeed |km/hr |Average speed in a time segment considering only the instances labeled as Moving.
|varspeed |km/hr |Speed variance in a time segment considering only the instances labeled as Moving.
|circadianmovement |- | \"It encodes the extent to which a person's location patterns follow a 24-hour circadian cycle.\" [Doryab et al.](../../citation#doryab-locations).
|numberofsignificantplaces |places |Number of significant locations visited. It is calculated using the DBSCAN clustering algorithm which takes in EPS and MIN_SAMPLES as parameters to identify clusters. Each cluster is a significant place.
|numberofsignificantplaces |places |Number of significant locations visited. It is calculated using the DBSCAN/OPTICS clustering algorithm which takes in EPS and MIN_SAMPLES as parameters to identify clusters. Each cluster is a significant place.
|numberlocationtransitions |transitions |Number of movements between any two clusters in a time segment.
|radiusgyration |meters |Quantifies the area covered by a participant
|timeattop1location |minutes |Time spent at the most significant location.
@ -146,3 +146,6 @@ Features description for `[PHONE_LOCATIONS][PROVIDERS][DORYAB]`:
**Fine Tuning Clustering Parameters**
Based on an experiment where we collected fused location data for 7 days with a mean accuracy of 86 & SD of 350.874635, we determined that `EPS/MAX_EPS`=100 produced closer clustering results to reality. Higher values (>100) missed out some significant places like a short grocery visit while lower values (<100) picked up traffic lights and stop signs while driving as significant locations. We recommend you set `EPS` based on the accuracy of your location data (the more accurate your data is, the lower you should be able to set EPS).
**Duration Calculation**
To calculate the time duration component for our features, we compute the difference between the timestamps of consecutive rows to take into account sampling rate variability. If this time difference is larger than a threshold (300 seconds by default) we replace it with a maximum duration (60 seconds by default, i.e. we assume a participant spent at least 60 seconds in their last known location)