its showing inner matrix dimensions must agree...i want the program to run for all values of N...how can i do that..???

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ASUTOSH 2014-2-1

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关闭： MATLAB Answer Bot 2021-8-20

ER = 1.0;
EO = 8.8541e-12;
VO = 1.0;
AA = 0.001;
L = 1.0;
N = 20;
DELTA = L/N;
% SECOND, CALCULATE THE ELEMENTS OF THE COEFFICIENT
% MATRIX A
I=1:N;
Y=DELTA*(I-0.5);
for i=1:N
    for j=1:N
        if(i ~=j)
            A(i, j)=DELTA/abs(Y(i)-Y(j) ) ;
else
A(i,j)=2.0*log(DELTA/AA);
end
end
end
% NOW DETERMINE THE MATRIX OF CONSTANT VECTOR B
% AND FIND Q
B = 4.0*pi*EO*ER*VO*ones(N,1);
C = inv(A);
RHO = C*(B);
SUM = 0.0;
for I=1:N
SUM = SUM + RHO(I);
end
Q=SUM*DELTA;
% FINALLY PLOT RHO AGAINST Y
plot(Y,RHO)
xlabel('y (cm)'), ylabel('rho_L (pC/m)')

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ASUTOSH 2014-2-1

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this is the code i have used ...please help me with the answer i want to run it for all values of N...it is throwing error that inner matrix dimensions must agree

ER = 1.0;

EO = 8.8541e-12;

VO = 1.0;

AA = 0.001;

L = 1.0;

N = 20;

DELTA = L/N;

% SECOND, CALCULATE THE ELEMENTS OF THE COEFFICIENT

% MATRIX A

I=1:N;

Y=DELTA*(I-0.5);

for i=1:N

    for j=1:N
        if(i ~=j)
            A(i, j)=DELTA/abs(Y(i)-Y(j) ) ;

else

A(i,j)=2.0*log(DELTA/AA);

end

% NOW DETERMINE THE MATRIX OF CONSTANT VECTOR B

% AND FIND Q

B = 4.0*pi*EO*ER*VO*ones(N,1);

C = inv(A);

RHO = C*(B);

SUM = 0.0;

for I=1:N

SUM = SUM + RHO(I);

end

Q=SUM*DELTA;

% FINALLY PLOT RHO AGAINST Y

plot(Y,RHO)

xlabel('y (cm)'), ylabel('rho_L (pC/m)')

Walter Roberson 2014-2-1

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

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Answer 1

Wayne King 2014-2-1

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https://ww2.mathworks.cn/matlabcentral/answers/114499-its-showing-inner-matrix-dimensions-must-agree-i-want-the-program-to-run-for-all-values-of-n-how#answer_122955

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It seems to work for a number of choices. Perhaps you have left over a matrix (for example A) in your workspace and then choose a smaller value of N so that A did not reduce in size?

For example, if you run the code above first with N=20 and then try N<20, like N=10

you will error because A will still be 20x20.

Try clearing all the variables in your workspace, or at least clear A using

clearvars A

and try again.