...
Currently the level, date and time can only be used for filtering (or can be extracted into Vector variables for other uses). They must be present in the file but you can specify any dummy value if you do not intend to use them.
Operations between geopoints and fieldsets
When you carry out an operation between geopoints and fieldset (or images) variables the result is another geopoints variable :
- When operating with fieldsets, the values of the field(s) at the geopoints locations are calculated by interpolation and the resulting field values undergo the operation with the geopoints values
- When combining with an image no interpolation takes place; the pixel values where the geopoints are located are extracted and these undergo the operation with the geopoints values
- Unless otherwise stated in the operator or function description, only the first value of a two-valued geopoint is considered during a calculation
Combinations include algebraic operations, boolean operations and a number of functions. See Geopoints Functions for details.
Missing values in geopoints
When you combine fieldset data with geopoints, you may end up with some missing values in your geopoints variable. These will have the value contained in the built-in global variable geo_missing_value. Any operation on a geopoints variable will bypass missing values (e.g. mean()) or retain them unaltered (e.g. max()); see individual function descriptions for more details.
In order to remove missing values from a geopoints variable, use the function remove_missing_values() as illustrated below:
geo_clean = remove_missing_values (geo_source)