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vector or list surrounding_points_indexes ( fieldset,list[,string] )Anchor surrounding_points_indexes surrounding_points_indexes
vector or list surrounding_points_indexes ( fieldset,number,number[,string] )
vector or list surrounding_points_indexes ( fieldset,vector,vector[,string] )
Returns the indexes of the four gridpoints surrounding the given location, ordered by increasing distance from the target point. If a list is given, it must contain two numbers - latitude and longitude. If two numbers are given, the first is the latitude, the second the longitude. The field must be a gridded field. If the fieldset has only one field, a single vector of indexes is returned; otherwise a list of vectors is returned. In the case where the field is a reduced Gaussian grid and the input location is at the North or South pole, beyond the most extreme row of points, there will be a 'circle' of surrounding points, and all of these indexes are returned.
For batch processing of multiple locations, two vectors can be given, the first is a vector of latitudes, the second the longitudes; this can be much more efficient than multiple calls with a single location each. If the fieldset has only one field, a single vector is returned; otherwise a list of vectors is returned.
By default, if any of the surrounding points are missing, the function will return nil. To prevent this, and to return all the points regardless, add the option 'all' as the last parameter of the function call.
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