Error message when running code: "Dimension argument must be a positive integer scalar"

Question

Abdalrazzaq Aljammal 2022-11-14

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1850813-error-message-when-running-code-dimension-argument-must-be-a-positive-integer-scalar

回答： Image Analyst 2022-11-15

在 MATLAB Online 中打开

I have this error message and i don't know what to do please help?

Error using size

Dimension argument must be a positive integer scalar or a vector of positive integers.

Error in practice (line 36)

x=zeros(size(n,q));

The code:

clear;
m1=3000;k=13650;
mass=[m1,0,0;0,4*m1,0;0,0,m1];
M=input('mass');
[n,o]=size(M);
if n~=o 
    error('mass');
end
stiff=[k+k,-k,0;-k,k+k,-k;0,-k,k+k];
K=input('stiff');
[n,o]=size(K);
if n~=o 
    error('stiff');
end
qu=0;
[u,l]=eig(K,M);
% Using eigin this way allows us to subtract M*w^2
% from K, instead of I*w^2 (where I is the n by n identity
% matrix).
% The output from eiggives unit-length eigenvectors.
% We need to scale them with respect to M.
%
for s=1:n
    alfa=sqrt(u(:,s)'*M*u(:,s));
    u(:,s)=u(:,s)/alfa;
end
inid=[0;0;0];
iniv=[0;0;0];
x0=input('inid');
xd0=input('iniv');
final=[];
tf=input('final');
t=0:0.1:tf;
q=tf/0.1;
x=zeros(size(n,q));
% Applying Equation 7.183.
%
for j=1:n
    w(j)=sqrt(l(j,j));
    xt=u(:,j)*(u(:,j)'*M*x0*cos(w(j).*t)+u(:,j)'*M*xd0/...
        w(j)*sin(w(j).*t));
    x=x+xt;
end
% Plotting the modes in a subplot format.
% Note that, for more than 3 or 4 degrees
% of freedom, the plots will become nearly
% unreadable.
%
for r=1:n
    subplot(n,1,r)
    plot(t,x(r,:))
    xlabel('Time, seconds');
    ylabel(['Response x',num2str(r)]);
end