Wrong answer from using UNIQUE function

I use the following codes to get a row vector and then unique it. But the answer is wrong.

• _v=3;alpha=0.5;i=1;for a=0:0.1:v for b=0:0.1:3-a x1=a; x2=b; x3=3-a-b; u(i)=x1-alpha*(x2-x1)-alpha*(x3-x1); i=i+1; endendunique(u)

Following is part of the answer:

-1.50000000000000  -1.25000000000000  -1.25000000000000  -1  -1.00000000000000  -1.00000000000000  -0.750000000000000  -0.750000000000000  -0.750000000000000  -0.750000000000000   ...

The result is definitely wrong. But I cannot find where the problem is. I'm a little crazy...

Anyone helps me is greatly appreciated.

Answer 1

[Star Strider]

If that was how you unique, you did not call it correctly. If you want to know everything about the unique rows of u, call it as:

[C,ia,ic] = unique(u,'rows');

The documentation explains the three outputs and how to use them.

Your vector u turns out to be a row vector, so to call unique using the 'rows' argument, transpose it:

v=3; 
alpha=0.5; 
i=1; 
for a=0:0.1:v 
    for b=0:0.1:3-a 
        x1=a; 
        x2=b; 
        x3=3-a-b; 
        u(i)=x1-alpha*(x2-x1)-alpha*(x3-x1); 
        i=i+1; 
    end 
end

[C,ia,ic] = unique(u','rows');

[jiahua]

Thank you! It works.

[Star Strider]

My pleasure!