The first character of a GMString specifies the type of local model to use during regression. EYE supports five types of local model:
The second character of a GMString specifies how much smoothing the function approximator uses. This ranges from 0 (no smoothing at all) to 9 (a fully global model). For values from 1 to 8, the data is partially smoothed: the local model is built from data weighted by a gaussian centered at the current query point. The smaller the standard deviation of the gaussian, the more the data will be biased toward points close to the query, hence the more local the model. For a value of 8, the standard deviation is set to one half of the width of the input space; for a valye of 7, the standard deviation is set to one quarter of the width of the input space; each time the number drops by one, the standard deviation is halved again. Hence a value of 1 represents a very local model with almost no smoothing, and a value of 8 leads to considerable smoothing.
The third character of a GMString specifies how many nearest neighbors to ensure are included in the local regression. If this is, say, three, then the three nearest neighbors of a query point will always be fully weighted when making predictions, even if they aren't particularly close to the query point.
Returning to our example GMString, L24:SN:93-9, we can now see that it represents a function approximator that uses locally linear regression, with little smoothing, and that always weights the four nearest neighbors fully.