Mean filters

Syntax: | `FILTER\MEAN x f npt`

If the `\MEAN` qualifier is used, the filter will be the running mean, or average, filter. This filter method is sensitive to large spikes in the data. Any large spikes, for example, `>∼1000` times normal value, should first be removed, by, for example, the median filter.

There are two versions of the running mean filter, which are chosen by whether `npt` is positive or negative. The window width is always `|npt|`.

If `npt > 0`, the average value of each window placement is calculated by summing the relevant points and dividing by `npt`. The averaging window butts up against the end.

If `npt < 0`, a much faster method is used which adds a new point to the right and drops an old one from the left. The window runs off half way from each end, but pseudo points outside the range are set to the appropriate end point values.

Median filters
Nonrecursive filters