Illegal use of reserved keyword "else".

Question

Craig Johnson 2021-12-2

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1600990-illegal-use-of-reserved-keyword-else

编辑： DGM 2021-12-2

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

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Chunru 2021-12-2

What are your edited code and the error message?

Craig Johnson 2021-12-2

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

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Answer 1

KSSV 2021-12-2

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1600990-illegal-use-of-reserved-keyword-else#answer_845505

编辑：KSSV 2021-12-2

在 MATLAB Online 中打开

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

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显示 1更早的评论隐藏 1更早的评论

KSSV 2021-12-2

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

KSSV 2021-12-2

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

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Answer 2

DGM 2021-12-2

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1600990-illegal-use-of-reserved-keyword-else#answer_845515

编辑：DGM 2021-12-2

在 MATLAB Online 中打开

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)) % ??