Illegal use of reserved keyword "else".

function q_P = ParticularSolution (K,M,f_0,t,w_R,roadflag)



Q=[[-K,-w_R*M,w_R*M,-K]
    
else roadflag==1
s_1==-f_0./K
s_2==0/K
q_P==s_1+s_2*t
elseif roadflag==2
    q_P==s_1*sin(w_R*t)+s_2*cos(w_R*t)
    s_1==s_2==F./Q
end

[Chunru]

The code has no "if" before "else". You have missed some codes before "else".

[Craig Johnson]

even with the first else edited to if it still flags it

[Chunru]

What are your edited code and the error message?

[Craig Johnson]

function q_P = ParticularSolution (K,M,f_0,t,w_R,roadflag)

Q=[[-K,-w_R*M,w_R*M,-K]

if s_1==-f_0./K

s_2==0/K

q_P==s_1+s_2*t

elseif roadflag==2

q_P==s_1*sin(w_R*t)+s_2*cos(w_R*t)

s_1==s_2==F./Q

end

end

Answer 1

[KSSV]

function q_P = ParticularSolution (K,M,f_0,t,w_R,roadflag)

Q=[-K,-w_R*M,w_R*M,-K] ;
    
if roadflag==1
s_1==-f_0./K
s_2==0/K
q_P==s_1+s_2*t
else roadflag==2
    q_P==s_1*sin(w_R*t)+s_2*cos(w_R*t)
    s_1==s_2==F./Q
end

[Craig Johnson]

still says illegal use

[KSSV]

Where are you using it? Show us the full code which you are using and throwing error.

[KSSV]

Editted the code....there is a typo error extra brace.

Answer 2

[DGM]

Start with

function q_P = ParticularSolution (K,M,f_0,t,w_R,roadflag)
Q = [-K,-w_R*M,w_R*M,-K]; % fix imbalanced brackets
    
if roadflag==1 % start with if
    s_1 = -f_0./K; % = is an assignment; == is a logical test
    s_2 = 0/K; % this is just zero ??
    q_P = s_1+s_2*t;
elseif roadflag==2
    q_P = s_1*sin(w_R*t) + s_2*cos(w_R*t);
    s_1 = s_2==(F./Q); % unused; F is undefined
end
end % close function scope

Observe that s_1 and s_2 are used in both cases, but are only defined in the first case. If these are indeed needed by both, move them outside the conditional structure.

Also, the size of the variables is likely to matter, but we don't know what they are. We know that Q is a vector. if F and s_2 are scalars, then

s_1 = s_2==(F./Q)

will return a logical vector. If either F or s_2 are vectors, their size would need to be compatible with that of Q. Again, since this assignment occurs after the assignment of the only output variable, the results are never used for anything. If it's to be moved before the assignment of q_P, then it remains to be seen how a logical vector would make conceptual sense in the calculation or whether the variable dimensions would be compatible.

Perhaps this is supposed to be an indexing operation, but I can only really guess at this point.

s_1 = s_2(s_2==(F./Q)) % ??