function [x_offset, y_offset] = get_fixation_offset(eye_x, eye_y, event_marker, fixation_event_marker, fixation_x, fixation_y)
% [x_offset, y_offset] = get_fixation_offset(eye_x_pos, eye_y_pos, event_marker, fixation_event_marker, fixation_x, fixation_y)
% 
% Estimates the x, and y-offset between screen position and reported eye position while fixating
%
% Arguments: 
%            eye_x, eye_y: The eye positions reported by the tracker, vectors of coordinates
%            event_marker: vector, the recorded event markers 
%            fixation_event_marker: scalar, the event marker that represents the fixation period
%            fixation_x, fixation_y: scalar, the x and y position of the fixation cross on the screen
%            
% Returns:
%            x_offset, y_offset: scalar the deviation between reported x
%            and y positions and the true positions.

eye_fixation_x_pos = median(eye_x(event_marker == fixation_event_marker));
eye_fixation_y_pos = median(eye_y(event_marker == fixation_event_marker));

x_offset = fixation_x - eye_fixation_x_pos;
y_offset = fixation_y - eye_fixation_y_pos;