i want to find k for different values of w using determinants, after that i want to find y2 for the different values but y2 cannot be executed

Question

Rosalinda 2023-11-9

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2045142-i-want-to-find-k-for-different-values-of-w-using-determinants-after-that-i-want-to-find-y2-for-the

移动：Steven Lord 2023-11-9

采纳的回答： Steven Lord

在 MATLAB Online 中打开

%finding k for different values of w

syms k

c44=44;

i=sqrt(-1);

w=1:3;

y1=zeros(1,length(w));

s=sym(zeros(1,length(w)));

p=sym(zeros(1,length(w)));

q=sym(zeros(1,length(w)));

y=sym(zeros(1,length(w)));

for j=1:length(w)

s(j)=c44*exp(k)*w(j);

p(j)=c44/w(j);

q(j)=c44+w(j)*i/k^2;

A=[c44*s(j) 2;p(j) q(j)];

z=det(A);

y(j)=vpasolve(z,k);

disp(y)

y1=real(y);

%relation between y1(or value of k) and w

y2(j)=w/y1(j);

end

Unable to perform assignment because the indices on the left side are not compatible with the size of the right side.

Error in sym/privsubsasgn (line 1200)
L_tilde2 = builtin('subsasgn',L_tilde,struct('type','()','subs',{varargin}),R_tilde);

Error in indexing (line 1031)
C = privsubsasgn(L,R,inds{:});

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Answer 1

Steven Lord 2023-11-9

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2045142-i-want-to-find-k-for-different-values-of-w-using-determinants-after-that-i-want-to-find-y2-for-the#answer_1349742

在 MATLAB Online 中打开

w is a vector.

w=1:3
w = 1×3
     1     2     3

y1(j) is a scalar. For purposes of this example I'll show a "dummy" y1 vector.

y1 = [4 5 6];
j = 1;
y1(j)
ans = 4

What do you get when you divide w by y1(j)? What size is that result?

result = w/y1(j)
result = 1×3
    0.2500    0.5000    0.7500

y2(j) is also a scalar (a 1-by-1 array.)

Can you stuff a 1-by-3 vector into a 1-by-1 array? To use a metaphor, can you fit three eggs into the same cup of an egg carton (without scrambling them)? No, you can't. So MATLAB throws an error when you try.

Perhaps you meant to divide w(j) by y1(j)?