readBEQI: Read BEQI input files
In BEQI2: Benthic Ecosystem Quality Index 2

This function reads and checks BEQI input files. The format has been specified in Van Loon (2013).

1	readBEQI(filename)

filename

name of BEQI input file (character)

The function performs the following tasks:

checks the existence of filename;
checks availablitity of required columns (case insensitive);
make column names with aggregation data case-insensitive;
removes redundant spaces;
checks if DATE-field adheres to ISO 8601 (YYYY-mm-dd);
constructs a unique identifier ID by concatenating columns OBJECTID and DATE;
aggregate (by summation) VALUE-fields of records that only differ in VALUE-field value;
checks that each ID has a unique AREA;
checks azoic samples for VALUE=0;
removes records with VALUE=0, not belonging to azoic samples;
checks VALUE-field on missing values;
checks if VALUE-field is an integer;