Increasing

The Increasing metafeature detects when a continuous signal is increasing. It operates on continuous values only. The output from Increasing is a list of tuples consisting of four parameters:

• midTime: The middle point temporally of the event. May be expressed in either frame number or relative representation (where the beginning of the stream is 0 and the end is 1); depending on the useRelativeTime setting.
• average: The average value of the event. This value is expressed in terms of the data type of the channel. If the useRelativeHeight parameter is true then this average is expressed as height above or below the mean of the channel for this training instance.
• gradient: This is the rate of change of the channel. To be exact, a line of best fit is fitted to the increasing interval, and the gradient of the line is calculated.
• duration: This is the length of the increasing interval. May be expressed in either number of frames or in a relatively (where the whole stream has a duration of 1) depending on the useRelativeTime setting.

It operates on a single channel. It accepts the following settings:

• channel: Which channel to extract increasing intervals from. Default value is the first channel defined in the domain description file.

• exceptions: Because of noise, it may occur that there are two intervals of increase separated by one noisy sample. Were it not for the noise, this would be considered one increasing interval. We may wish to allow a certain number of exceptional samples which do not meet the strictly increasing property. Default value is 1.

• useRelativeTime: Time measures (in particular duration and midtime) can be expressed either in absolute terms (i.e. if it happens at the 19th frame, it occurs at time 19), or relative terms (if it occurs at the 19th frame, and the whole stream is 38 frames long, then it happens halfway along the stream). Using relative time improves robustness to linear temporal variation, but loses absolute temporal information. Default value is false.
• useRelativeHeight: Just as for time measures, average values can be expressed in absolute (i.e. average value for this interval is 1.3) or relative terms (the average for the increasing interval is 0.3 higher than the mean of the channel). Default value is false.
• minDurn: This is the shortest duration signal (in frames) that will be accepted as an increasing interval. If there is a increasing interval shorter than this, it is not considered. Default value is 3 frames.