Matrix dimensions must agree

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Meaghan
Meaghan 2017-10-17
回答： Gautam 2024-10-23，4:49
Hi, I am having trouble with solving a system of linear equations. I am getting an error that the matrix dimensions must agree and i cannot divide a/b.
if true
x1=167.48;
x2 = 355.63;
x3 = 355.63;
x4=264.58;
x5=62.93;
x6=167.48;
a= 1000.*(6+.005.*x1)./1.1 ;
b= 1000.*(6+.005.*x2)./1.1 ;
c= 1000.*(6+.005.*x3)./1.1 ;
d= 1000.*(6+.005.*x4)./1.1 ;
e= 1000.*(6+.005.*x5)./1.1;
f= 1000.*(6+.005.*x6)./1.1;
g= (1000.*(6+.005.*x1)/1.1).^-1;
h= (1000.*(6+.005.*x2)/1.1).^-1;
i= (1000.*(6+.005.*x3)/1.1).^-1;
j=(1000.*(6+.005.*x4)/1.1).^-1 ;
k=(1000.*(6+.005.*x5)/1.1).^-1;
l=(1000.*(6+.005.*x6)/1.1).^-1 ;
r = -.0024
a = [1,0,0,0,0,0, 0,0,0,0,0,0, g,0,0,0,0,0 0,0,0,0,0,0;
0,1,0,0,0,0, 0,0,0,0,0,0, 0,h,0,0,0,0 0,0,0,0,0,0;
0,0,1,0,0,0, 0,0,0,0,0,0, 0,0,i,0,0,0 0,0,0,0,0,0;
0,0,0,1,0,0, 0,0,0,0,0,0, 0,0,0,j,0,0 0,0,0,0,0,0;
0,0,0,0,1,0, 0,0,0,0,0,0, 0,0,0,0,k,0 0,0,0,0,0,0;
0,0,0,0,0,1, 0,0,0,0,0,0, 0,0,0,0,0,l 0,0,0,0,0,0;
r,0,0,0,0,0 1,0,0,0,0,0 0,0,0,0,0,0 0,0,0,0,0,0;
0,r,0,0,0,0 0,1,0,0,0,0 0,0,0,0,0,0 0,0,0,0,0,0;
0,0,r,0,0,0 0,0,1,0,0,0 0,0,0,0,0,0 0,0,0,0,0,0;
0,0,0,r,0,0 0,0,0,1,0,0 0,0,0,0,0,0 0,0,0,0,0,0;
0,0,0,0,r,0 0,0,0,0,1,0 0,0,0,0,0,0 0,0,0,0,0,0;
0,0,0,0,0,r 0,0,0,0,0,1 0,0,0,0,0,0 0,0,0,0,0,0;
0,0,0,0,0,0 a,0,0,0,0,0 0,0,0,0,0,0 1,0,0,0,0,0;
0,0,0,0,0,0 0,b,0,0,0,0 0,0,0,0,0,0 0,1,0,0,0,0;
0,0,0,0,0,0 0,0,c,0,0,0 0,0,0,0,0,0 0,0,1,0,0,0;
0,0,0,0,0,0 0,0,0,d,0,0 0,0,0,0,0,0 0,0,0,1,0,0;
0,0,0,0,0,0 0,0,0,0,e,0 0,0,0,0,0,0 0,0,0,0,1,0;
0,0,0,0,0,0 0,0,0,0,0,f 0,0,0,0,0,0 0,0,0,0,0,1;
0,0,0,0,0,0 0,0,0,0,0,0 0,0,0,0,0,0 1,0,0,0,0,-1;
0,0,0,0,0,0 0,0,0,0,0,0 0,0,0,0,0,0 0,1,0,0,0,-1;
0,0,0,0,0,0 0,0,0,0,0,0 0,0,0,0,0,0 0,0,1,0,0,-1;
0,0,0,0,0,0 0,0,0,0,0,0 0,0,0,0,0,0 0,0,0,1,0,-1;
0,0,0,0,0,0 0,0,0,0,0,0 0,0,0,0,0,0 0,0,0,0,1,-1;
0,0,0,0,0,0 0,0,0,0,0,0 1,1,1,1,1,1 0,0,0,0,0,0;];
% 1 2 3 4 5 6 7 8 9 101112131415161718192021222324
b = [0;0;0;0;0;0;0;0;0;0;0;0;0;0;0;0;0;0;0;0;0;0;0;0;];
x= size(a)
z = size(b)
y = a/b
end

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回答（2 个）

KSSV
KSSV 2017-10-17
Replace:
y = a/b
with
y = a\b
Gautam
Gautam 2024-10-23，4:49
Hello Meaghan,
The reason you get this error is because you cannot divide two matrices the way you divide two scalars.
To find the solution to a system of linear equations, use the “\” operation instead of “/”. Like, “y = a\b”
Hope this helps

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