Frequency of appearance of individual features in selected feature sets.

<p>The y-axis indicates the number of {sensors∶time points} used. For example, 4∶1 represents finding optimal subset of 4 sensors and 1 time point in each sensor. The rows in between the labels on the y-axis represents the other options for the number of time points (e.g. the rows between 4∶1 and 5∶1 are {4∶2, 4∶3, 4∶4, 4∶5, 4∶6} respectively. The x-axis marks the identities of the sensors and time points that were used. Colours represent the frequency (%) with which a {sensor∶time point} combination was chosen, as shown in the colour scale.