Example of how to include the event categories within the registrations csv output.

functions.php

<?php //Please do not add the opening PHP tag if you already have one.

function ee_tw_event_categories_to_csv( $reg_csv_array, $reg_row ) {
	$EVT_ID = $reg_row['Registration.EVT_ID'];
 	$terms = array();
	$event_categories = get_the_terms( $EVT_ID, 'espresso_event_categories' );
	if ( $event_categories ) {
		foreach( $event_categories as $term ) {
			$terms[] = $term->name;
		}
		$terms = implode( ', ', $terms);
	}
	$reg_csv_array['Event Categories'] = !empty($terms) ? $terms : null;
	return $reg_csv_array;
}
add_filter( 'FHEE__EventEspressoBatchRequest__JobHandlers__RegistrationsReport__reg_csv_array', 'ee_tw_event_categories_to_csv', 10, 2 );