Why the mod function does not work

My code started with 0 degree but when it gets only 180 and than it get 170, 160 and so on ... I would like it to 2pi (360 degrees)

for f=1:h
    t=(f-1)*k/20;
    m=f+1;
    P0=[70 70]; %střed [x,y]
    P1=[htabulka(1,1),htabulka(1,2)]; %XY1 [x,y]
    P2=[htabulka(f,1),htabulka(f,2)]; %XY2 [x,y]
    %angstn=wrapTo2Pi(atan2(abs((htabulka(1,1)-60)*(htabulka(f,2)-60)-(htabulka(f,1)-60)*(htabulka(1,2)-60)),(htabulka(1,1)-60)*(htabulka(f,1)-60)+(htabulka(1,2)-60)*(htabulka(f,2)-60)));
    
    angstn =mod(atan2(norm(det([P2-P0;P1-P0])),dot(P2-P0,P1-P0)),2*pi);
    
    
    %angst= angstn * (angstn >= 0) + (angstn + 2 * pi) * (angstn < 0);
    ang=angstn*180/pi
    cosf=cos(ang);
    

[Eliska Paulikova]

This is the output

[Torsten]

Is it better what you get from this code ?

for f=1:h
    t=(f-1)*k/20;
    m=f+1;
    P1=[70 70]; %střed [x,y]
    P2=[htabulka(1,1),htabulka(1,2)]; %XY1 [x,y]
    P3=[htabulka(f,1),htabulka(f,2)]; %XY2 [x,y]
    angstn = atan2(P3(2) - P1(2), P3(1) - P1(1)) - atan2(P2(2) - P1(2), P2(1) - P1(1));
    if angstn < 0
        angstn = angstn + 2*pi;
    end
    ang=angstn*180/pi
    cosf=cos(ang);

Answer 1

[Walter Roberson]

angstn =mod(atan2(norm(det([P2-P0;P1-P0])),dot(P2-P0,P1-P0)),2*pi);

norm() is always non-negative, so you are taking atan2() in the case where y is positive and x is potentially either positive or negative. That is always going to give you a result between 0 and pi, so the mod() against 2*pi is always going to just return the same value.