Variable 'D' is not fully defined on some execution paths. Why?

Hello. I'm using the following code in embedded matlab in simulink. And I,m getting the message that Variable 'D' is not fully defined on some execution paths. And i don't know what is the problem in code.

function D = mpp(V,I,T)
  Dinit = 0.7;
  delD = 0.001;
  Dmax = 0.9;
  Dmin = 0.1;

    persistent P0 V0 D0 n;

    if isempty(P0)
        P0 = 0;
        V0 = 0;
        n = 1;
        D0 = Dinit;
    end

    P = V*I;

    dP = P - P0;
    dV = V - V0;

    if(T>0.02*n)
        n=n+1;

        if(dP*dV > 0)
            D = D0 - delD;
        elseif(dP*dV < 0)
            D = D0 + delD;           
        end
    else
        D = D0;
    end

    if D>=Dmax | D<=Dmin
        D = D0;
    end

    V0 = V;
    P0 = P;
    D0 = D;

Answer 1

[Walter Roberson]

        if(dP*dV > 0)
            D = D0 - delD;
        elseif(dP*dV < 0)
            D = D0 + delD;           
        end

does not assign to D if dp*dV == 0

[Soham Delvadia]

Steel it shows the same message for the following portion of code as before

if D>=Dmax | D<=Dmin

[Walter Roberson]

What did you change the code to? The code you posted has a problem in the situation that dP == 0 or dV == 0.

[小东 刘]

hello! now I have the same problem. How did you change it ?

[Steven Lord]

Look at the simple example below. What does fun343107 do when x is exactly equal to 0? That behavior is undefined, so you'll receive a similar type of error as the original poster. To fix it, add code to handle the case where x is exactly equal to 0 in fun343107; that's the code that's commented out in the function.

Look for this same type of situation in your code.

y = fun343107(1)

y = 'positive'

y = fun343107(-1)

y = 'negative'

y = fun343107(0)

Output argument "y" (and possibly others) not assigned a value in the execution with "solution>fun343107" function.

function y = fun343107(x)
if x > 0
    y = 'positive';
elseif x < 0
    y = 'negative';
% else
%   y = 'zero';
end
end