If statement is not working

Hi,

angle1 variable has data from 0 to 90 but is statemant is not working. For example if angle1>=3 and if angle1>=53 give same results.

I do not understand what is the problem.

Thank you...

angle1=abs(atand((newVar(:,3)-newVar5(:,3))./(newVar(:,1)-newVar5(:,1))))
[~,idx5] = pdist2(newVar2,newVar,'euclidean','smallest',1);                 % indices of nearest * for EACH X
newVar6=newVar2(idx5, :);
angle2=abs(atand((newVar6(:,3)-newVar5(:,3))./(newVar6(:,1)-newVar5(:,1))))
d2=pdist2(newVar5,newVar6);
dy=d2(:)
if angle1>=19
    dxs=(sind(angle1).*dx);
    dys=(sind(angle2).*dy);
    def=dxs-dys
else
    dxs=(cosd(angle1).*dx);
    dys=(cosd(angle2).*dy);
    def=dxs-dys
end

[Chad Greene]

What are the newVars?

[Mehmet Volkan Ozdogan]

newVars is a matrice 100x3. they are coordinates...

Thanks

Answer 1

[Walter Roberson]

In MATLAB, the test

if A > B

is treated the same as if it had been

if all(A(:) > B(:))

Your angle1 is a vector. Some of the elements of it are >= 19, but not all >= 19, so the if is not considered to be true.

When you are working with non-scalars, you should get in the habit of explicitly coding all() or any() to indicate which test you intend.

... But what you probably really need is to learn about logical indexing: see https://blogs.mathworks.com/steve/2008/01/28/logical-indexing/

[Mehmet Volkan Ozdogan]

Thank you for your answer,

If i understand correctly, now i have changed the line as if all(angle1(:)>=19)

but still if statement is not working.

[Walter Roberson]

The existing code is already equivalent to that. But remember that it means that if each and every value in the array is >= 19 then you want to do something, and that if even one value in the array is < 19 then you want to do something else completely.

Might I suggest that you instead want to do one thing for the values that are >= 19 and something else for the values that are < 19 ? That calls for a loop, or better yet for logical indexing.

[Mehmet Volkan Ozdogan]

The values in angle1 are varies from 0 to 90..

And i have changed the code like given below;

if all(angle1(:)>19)
    dxs=(sind(angle1).*dx);
else
    dxs=(cosd(angle1).*dx);
end
if all(angle1(:)>=19)
    dys=(sind(angle2).*dy);
else
    dys=(cosd(angle2).*dy);
end
def=dxs-dys

but still if statement is not working..

Actually, the values in angle1 is a float number and has 20 decimal. Is that be the reason?

Thank you

[Rik]

Try to find a tutorial in your native language that explains loops and logical indexing.

Your code has every indication that you should be using that instead.

[Mehmet Volkan Ozdogan]

Thank you for your advices Mr. Roberson

I have now understand what you mean and solved my problem

for i=(1:100)
  if all(angle1(i)>=19)
    dxs(i)=(sind(angle1(i)).*dx(i));
    dys(i)=(sind(angle2(i)).*dy(i));
   else
    dxs(i)=(cosd(angle1(i)).*dx(i));
    dys(i)=(cosd(angle2(i)).*dy(i));
  end
   def(i)=dxs(i)-dys(i)
end

[Walter Roberson]

Example:

Mask = x> 5;
Y(Mask) = sin(x(Mask))
Y(~Mask) = cos(x(~Mask))