When a table is filtered, only valid rows satisfying these expressions are passed through for processing. When row filters are passed in bracket notation in this manner, the filtering is set up automatically when the file is opened and all processing occurs through the filter.
Programs also can use the filter library API to open filters explicitly.
Table filtering can be performed on columns of data in a FITS binary table or a raw event file. Table filtering is accomplished by means of table filter specifications . A single filter expression consists of an arithmetic, logical, or other expression generally involving one or more column values from a table. Table filtering is more easily described by means of examples. When such a separator is used, the boolean AND operator is automatically generated in its place.