QCQP error of fmincon: Row dimension of A is inconsistent with length of b.

I have the following problem and I need to minimize the cost C with these constraints:

% Minimize C(dp)

% Decision variable = dp

% subject to:

% R(dp) >= C(dp)

% w >= 0

% pmin*l <= (po*l + dp) <= pmax*l % not needed

% l*dp <= 0 % not needed

I got the following error:

Error using fmincon (line 307)

Row dimension of A is inconsistent with length of b.

Please, help!

% po is constant price dollars per cubic feet $/CF
po = 3;
%  is a vector of price for each hour
p = zeros(1,24);
% dp is a vector of price change from the default price po
dp = zeros(1,24); % Decision variable
% l is vector with all components one
l = ones(1,24);
% J is the price elasticity matrix (PEM)
J = zeros(24);
J = [-6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3; 
      3 -6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 -6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 -6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 -6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 -6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 -6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 -6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 -6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 -6 3 3 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 -6 3 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 -6 3 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 -6 3 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 -6 3 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 3 -6 3 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 -6 3 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 -6 3 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 -6 3 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 -6 3 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 -6 3 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 -6 3 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 -6 3 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 -6 3;
      3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 -6];
    

% f is a vector of the day-ahead demand forecast (for now, actual demand will be used)
% f = zeros(1,24);
% use D (actual demand) as f, for testing
D = [235.20	126.32	73.16	242.16	257.36	553.27	436.89	652.46	457.64	300.99	312.12	340.37	251.22	259.53	187.42	252.68	340.34	424.82	279.40	330.57	362.92	484.82	229.90	231.88];
f = D;
% Definde p & w
p = po .* l + dp;
% w is the water use profile
w = f + J .* dp;
%% Utility parameters
% Cost coefficients
b = 1000;
c = zeros(1,24);
c = 2.2*l;
d = 1;
wt = 140;
pmin = 1;
pmax = 5;
o = zeros(1,24);
% Revenue R 
% Cost C
R = p.' .* w;
C = b + c.' .* w + d .* max(w - w.'.*l, o).' * max(w - w.'.*l, o); % Objective function

%% Optimization

% Minimize C(dp)
% Decision variable = dp 
% subject to:
%               R(dp) >= C(dp)
%               w >= 0
%               pmin*l <= (po*l + dp) <= pmax*l     % not needed
%               l*dp <= 0                           % not needed

A = C;
b = R;
dp0 = ones(1,24);
func = @C;

fmincon(func,dp0,A,b)

Answer 1

[Guru Mohanty]

Hi, I Understand you are trying to minimize C with the discission variable dp. To use fmincon function ie min(f) the condition is

" A*dp => b". In your case 'A' is a 24x24 matrix and 'dp' 1x24 matrix. 'B' should be a 24x1 matrix, but in your scenario, it is a 24x24 matrix. This leads to Dimension Inconsistency Error. After changing dimension the code should work.

[Faisal Alghamdi]

Thanks for your help.

I changed the size of B but the code still not working.

I am getting this error:

"Unrecognized function or variable 'C'."

B = R(:,1);