Variable "Flag" is not fully defined in some execution paths. Why?

function [Gs1, Gs2, Gs3] = mpp(Ppv, Po, T, Ipv, Vbat)

persistent Flag0

if isempty(Flag0)

Flag0 = 1; Flag = 1;

end

Vbnom = 45; Vbmax = 50;

if(mod(T,0.02)== 0)

while (Flag0 == 1)

while (Vbat <= Vbnom)

Gs1 = 1;

Gs2 = 1;

Gs3 = 0;

Flag = 2;

Flag0 = Flag;

return

end

while (Vbat > Vbnom)

Gs1 = 1;

Gs2 = 0;

Gs3 = 1;

Flag = 3;

Flag0 = Flag;

return

end

end

while (Flag0 == 2)

while (Ipv <= 0)

Gs1 = 0;

Gs2 = 0;

Gs3 = 1;

Flag = 1; Flag0 = Flag;

return

end

while (Ipv > 0)

while (Ppv >= Po)

while (Vbat >= Vbmax)

Gs1 = 1;

Gs2 = 0;

Gs3 = 1;

Flag = 3;

Flag0 = Flag;

return

end

while (Vbat < Vbmax)

Gs1 = 1;

Gs2 = 1;

Gs3 = 0;

Flag = 1; Flag0 = Flag;

return

end

end

while (Ppv < Po)

Gs1 = 1;

Gs2 = 0;

Gs3 = 1;

Flag = 3; Flag0 = Flag;

return

end

end

end

while (Flag0 == 3)

while (Ipv <= 0)

Gs1 = 0;

Gs2 = 0;

Gs3 = 1;

Flag = 1; Flag0 = Flag;

return

end

while (Ipv > 0)

while (Ppv > Po)

Gs1 = 1;

Gs2 = 1;

Gs3 = 0;

Flag = 2; Flag0 = Flag;

return

end

while (Ppv <= Po)

Gs1 = 1;

Gs2 = 0;

Gs3 = 1;

Flag = 3; Flag0 = Flag;

return

end

end

end

while (Flag0 > 3) || (Flag0 < 0)

Gs1 = 1;

Gs2 = 0;

Gs3 = 1;

Flag = 1; Flag0 = Flag;

end

else

Flag = 1;

Gs1 = 1;

Gs2 = 1;

Gs3 = 0;

end

Flag0 = Flag;

Answer 1

[Star Strider]

Because there are conditional statements in the code, and not all of them set the ‘Flag’ variable.

One way to avoid that is to set it to something at the beginning of the code, for example —

function [Gs1, Gs2, Gs3] = mpp(Ppv, Po, T, Ipv, Vbat)

Flag = NaN;

... REST OF THE CODE ...

end

or whatever default value for it makes sense in context.

.