Integration of anonymous functions using fmincon

Dear all,

I want to find the maximum area of a function subject to some constraints using fmincom.

Here is my code

b_method = [1/2, 1/2];
a_method = [0,0;1,0];


dim = size(a,1)

%the area of the  function is expressed as..
R=@(c)integral(@(z) 1+[z(1) z(2)].*b_method.*inv(eye(dim)-[z(1) z(2)].*a_method).*ones(dim,1),'ArrayValued', true);


%starting point
x0 = [-1,-1];

%p=1 constraints
a_c = [1,0;0,1];
b_c = [1;1];

x = fmincon(R,x0,a_c,b_c)

I am very new with using fmincon and this is the error I am getting

Error using integral (line 85)
A and B must be floating-point scalars.

Error in
maximize>@(c)integral(@(z)1+[z(1),z(2)].*b.*inv(eye(dim)-[z(1),z(2)].*a).*ones(dim,1),'ArrayValued',true)

Error in fmincon (line 552)
      initVals.f = feval(funfcn{3},X,varargin{:});

Error in maximize (line 22)
x = fmincon(R,x0,a_c,b_c)

Caused by:
    Failure in initial objective function evaluation. FMINCON cannot continue.

I am not sure where the error is coming from, any help would be appreciated.