How can i solve for this issue with the logical flow

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Mark Loui on 6 May 2021

Commented: Mark Louion 6 May 2021

Accepted Answer: Chad Greene

                          n=length(q);
                         
                          coef=k*dt/dr;
                         
                          q_new=zeros(n,1);
                         
                          q(0)=0;
                         
                          % for i=1:n+1
                         
                          % q_new(i)=q(i)+(coef*(q(i+1)-(2*q(i))+q(i-1)));
                         
                          % end
                         
                          fori=1:n+1
                         
                          term1=(q(i+1)*((r(i+1)+dr)/r(i)*dr));
                         
                          term2=2*q(i)*(1/dr);
                         
                          term3=q(i-1)*((r(i)-dr)/r(i)*dr);
                         
                          qnew(i)=q(i)+(coef*(term1-term2+term3));
                         
                          q_new=qnew(i);
                         
                          end

Can someone please help me with this i cant seem to make it work, what can i do to make the the error of logical go away?

数组索引必须是正整数或logical values: %This is the error show

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Accepted Answer

Chad Greene on 6 May 2021

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//www.tianjin-qmedu.com/matlabcentral/answers/823225-how-can-i-solve-for-this-issue-with-the-logical-flow#answer_693635

I think the error is here:

term3=q( i-1 )*((r(i)-dr)/r(i)*dr);

The first time through the loop, i=1 , meaning i-1=0 . There is no zeroth element of q. Which element of q are you trying to access?

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Mark Loui on 6 May 2021

Hmm sounds good, i try and see thanks

s manbetx 845

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