MATLAB: Size mismatch (size [1 x 11] ~= size [1 x 10]).

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Greetings to al my name JOSE LUIS HUAYNAY VILLAR, I have the following error problem;
Size mismatch (size [1 x 11] ~= size [1 x 10]).
the program indicates the error to me in this line, that seems strange to me
Function 'MATLAB Function3' (#169.624.635), line 21, column 17: "D(k+1)+D(j)" Launch diagnostic report.
and this is my code, please someone help me:
function dot_theta = fcn(theta,theta_0,theta_f)
dot_theta=size(10,1);
D=size(10,1);
K=size(10,1);
L=50;  %comprimento
z=linspace(0,L,10); 
theta_r = 0.218;     
alpha= 0.0115;     
K_s = 31.6;         
theta_s=0.52;      
dz=L/length(z);
b=1/(2*dz^2);
n = 2.03;
m=1-(1/n);
i=2:length(z),
j=1:length(z),
k=0:length(z),
D=(K_s*(1-m)/(alpha*m*(theta_s-theta_r)))*dot(theta,theta);
K=(K_s*(1-m)/(alpha*m*(theta_s-theta_r)))*dot(theta,theta);
dot_theta =b*((D(k+1)+D(j))*(theta(k+1)-theta(j))- b*(D(i-1)+D(j))*(theta(j)-theta(i-1))+((K(j)-K(i-1))/Delta_z));

Best Answer

i=2:length(z),
That is 2:10
j=1:length(z),
That is 1:10, which is one element longer than i.
D(i-1)+D(j)
D(i-1) becomes D(1 to length(z)-1) which is D(1 : 9)
D(j) is D(1:length(z)) which is D(1:10)
The two items are different lengths and cannot be subtracted.
You have similar problems for theta(k+1) vs theta(j)
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