Undefined function or variable

hi i am trying to make my own rgb-to-hsv function. this is my code.

    R=I(:,:,1);
    G=I(:,:,2);
    B=I(:,:,3);

    hue_one = mod((((G-B).*60)./(max(I,[],3)-min(I,[],3))),360);
    hue_two = (((B - R).*60)./(max(I,[],3)-min(I,[],3))) + 120;
    hue_three = (((R - G).*60)./(max(I,[],3)-min(I,[],3))) + 240;

    if (R == G) & (R == B)
        H = 0;
    elseif (R >= G) & (R >= B)
            H = hue_one; 
    elseif (G >= R) & (G >= B)
                H = hue_two;
    elseif (B >= R) & (B >= G)
                    H = hue_three;
    end

    V = max(I,[],3);

    if V == 0
        S = 0;
    else
        S = (max(I,[],3)-min(I,[],3))./max(I,[],3);
    end

    HSV(:,:,1) = H;
    HSV(:,:,2) = S;
    HSV(:,:,3) = V;

imshow(HSV)

values of S and V are loaded in the workspace without errors while the H returns an error.

Undefined function or variable 'H'.

Error in convertRGB (line 29)
HSV(:,:,1) = H;

i tried running my code line by line. after the if/elseif statements, there was no generated value of H. the variables hue_one, hue_two and hue_three also returned a matrix and can be found on the workspace pane. WHAT COULD HAVE BEEN THE PROBLEM OF THIS? THANK YOU.

Answer 1

[Kan-Hua]

I would suggest you add a "else" statement in your first "if" block. It may be that your RGB components of the image you loaded does not match any of the if-condiations in your block, and thus your H is not assigned to any value.

For example:

   if (R == G) & (R == B)
        H = 0;
    elseif (R >= G) & (R >= B)
            H = hue_one; 
    elseif (G >= R) & (G >= B)
                H = hue_two;
    elseif (B >= R) & (B >= G)
                    H = hue_three;
    else
          H=0; %or whatever
    end

Hope this helps. :)

Answer 2

[Wayne King]

What do you expect these comparisons to yield:

if (R == G) & (R == B)
        H = 0;
    elseif (R >= G) & (R >= B)
            H = hue_one; 
    elseif (G >= R) & (G >= B)
                H = hue_two;
    elseif (B >= R) & (B >= G)
                    H = hue_three;
    end

If these are false for any element of these matrices (very, very likely), then H is not assigned anything.