I am mistaken for angle

Dx=[451.1489;71.922;22.064;-52.849;-434.247] Dy=[423.253;290.384;292.965; 296.519;377.443]

[u m]=size(Dx);

for i=1:u t(i)=atan(Dy(i)/Dx(i))*200/pi; end

if Dx(i)>0 & Dy(i)>0 t(i)=t(i) elseif Dx(i)<0 & Dy(i)>0 t(i)=t(i)+200 elseif Dx(i)<0 & Dy(i)<0 t(i)=t(i)+200; elseif Dx(i)>0 & Dy(i)<0 t(i)=t(i)+400; end

The result is wrong; t= [47.970; 84.543; 95.214; -88.771; 154.448]

The correct result is; t= [47.970; 84.543; 95.214; 111.229; 154.448]

Is line 4 causing the error?

Answer 1

[Jan]

Note that you change the result outside the loop:

for i=1:u
  t(i)=atan(Dy(i)/Dx(i))*200/pi;
end   % <-- remove this

if Dx(i)>0 & Dy(i)>0
  t(i)=t(i)  % Omit this one :-)
elseif Dx(i)<0 & Dy(i)>0
  t(i)=t(i)+200
elseif Dx(i)<0 & Dy(i)<0
  t(i)=t(i)+200;
elseif Dx(i)>0 & Dy(i)<0
  t(i)=t(i)+400;
end
% end  % <-- insert an "end" here

When processed after the loop, only the last value of "i" is accessed.

Logical indexing will be more efficient:

t = atan(Dy ./ Dx) * (200/pi);   % elementwise: ./ 
index    = (Dx<0 & Dy>0);
t(index) = t(index) + 200;

and so on.

[Muhendisleksi]

thank you very, very much!