MATLAB: Fzero line 398 error; debugger not solving…

|| and && operatorsdebuggerfzero (line 398)

I am having a problem with fzero in this code :
prueba = r_teor (8e-3) 
function Arg = r_teor (t0)  
FC = 4.24E-1;     
a  = 6.05;         
FD = 8.17E-4;
Io = 15.53;
V  = 25.00;
texp=0.009:0.0001:0.0099;
      Arg         = zeros (N,1); % prellocating

      for i       = 1 : N
      options=optimset('Display','iter','TolX',1e-5);
      % Display: off / iter / final / notify
      % TolX: Default 2.204 e-16
      Arg   (i)   = fzero (@(r) trapecios (r) - (texp(i)-t0), 5e-3, options);
      end
          function Int = trapecios(r)
          if r <= 1    
            Int = 0;
            return
          end 
          F         = @(x) FC .* exp( -(V.*a) ./ (30.*x.*log(x)) );
          Int       = 0;
          part      = 1e-3;
          L         = 1:part:r;
          me        = F(L);
          sum_me    = sum (me);
          ue        = F( max( L ) );
          Int       = zeros (N,1); % prellocating
          i         = 1:N;
          Int   (i) = part.* (sum_me - (ue/2));
          end % trapecios
end % r_teor
The error is:
Operands to the || and && operators must be convertible to logical scalar values.
Error in fzero (line 398)
        if ~isfinite(fb) || ~isreal(fb) || ~isfinite(b)
, but the debugger sais that both b and fb are real and finite:
K>> b, fb, whos b, whos fb
b =
     1.163523750296039
fb =
     1.0e-03 *
    -0.999999999999276
    -0.999999999999276
    -0.999999999999276
    -0.999999999999276
    -0.999999999999276
    -0.999999999999276
    -0.999999999999276
    -0.999999999999276
    -0.999999999999276
    -0.999999999999276
    Name      Size            Bytes  Class     Attributes
    b         1x1                 8  double              
    Name       Size            Bytes  Class     Attributes
    fb        10x1                80  double
My function trapecios has no problem when executing it on b = 1.163523750296039.
Could it be because fzero cannot find zeros if the function does not change it sign (as x^2) ? Could it be because I must enter t0 as a 1:10 array (t0 is the variable of r_teor, so how could I do it) ?
Any idea? Thanks !!!

Best Answer

What requirement does fzero impose on the function you pass to it?
Function to solve, specified as a handle to a scalar-valued function or the name of such a function. fun accepts a scalar x and returns a scalar fun(x).
Does your function satisfy that requirement? In particular, does it return a scalar fun(x)?
If you want to solve a nonlinear system of equations, see fsolve in Optimization Toolbox.
Related Question