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Computes the mean of the geopoints. Missing values are bypassed in this calculation. If there are no valid values, then nil is returned.
geopoints nearest_gridpoint ( fieldset,geopoints )
Generates a set of geopoints from a field. The first field of the input fieldset is used. The result is a set of geopoints whose locations are from the original geopoints, but whose values are those of the nearest gridpoints in the field to the geopoints given as a second parameter. Where it is not possible to generate a sensible value due to lack of valid data in the fieldset, the internal geopoints missing value is used (this value can be checked for with the built-in variable geo_missing_value or removed with the function remove_missing_values).
geopoints offset ( geopoints,number,number )
geopoints offset ( geopoints,list)
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