computeEffectiveSpeed.m

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% Anne Urai and Klaus Wimmer, 2016
% anne.urai@gmail.com / kwimmer@clinic.ub.es

function speed = computeEffectiveSpeed(coord, display)
% computes temporal tuning parameter k, based on either the speed of the
% dots (in degrees/s) or a set of dot coordinates 

% compute the displacement per dot between each pair of successive frames
moved = nan(size(coord, 3), size(coord, 1) -1);
for d = 1:size(coord, 3),
    for f = 1:size(coord, 1)-1,
        % displacement in x and y direction
        vecX = diff(coord([f f+1], 1, d));
        vecY = diff(coord([f f+1], 2, d));
        % compute the resulting vector
        vecResult = sqrt(vecX.^2 + vecY.^2);
        moved(d, f) = vecResult;
    end
end
moved = moved(:);

% now compute the speed from this displacement
speed        = pix2deg(display, moved(:)) .* display.frameRate; 
speed        = median(speed); % most prevalent speed in this display

end