MATLAB: Operands to the || and && operators must be convertible to logical scalar values

fzerological scalar values

Hi everybody!
Why am I having this error and how can I solve it?
I have already about this error but cannot find the way to avoid it in my case…
Thanks!!!
options=optimset('Display','iter');
fzero (@(r) trapecios(r)-100, 1.21, options)
function Int = trapecios (r)
  FC = 4.24E-1;      % 0.424 para 25 V y 0.381 para 40 V
  a  = 6.05;         % 6.050 para 25 V y 4.730 para 40 V
  %FD = 8.17E-4;
  %Io = 15.53;
  V  = 25;
  %N=10;
  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       = part.* (sum_me - (ue/2));
end
The error is:
Operands to the || and && operators must be convertible to logical scalar
values.
Error in fzero (line 365)
        if ~isfinite(fa) || ~isreal(fa) || ~isfinite(a)
Error in Cesar_r_teor_trapecios (line 4)
fzero (@(k) trapecios(k)-100, 1.21, options)

Best Answer

LEARN TO USE THE DEBUGGER!!!!!!!!!
I did this:
dbstop if error
Next, I ran your code. Well, I tried to run it.
fzero (@(r) trapecios(r)-100, 1.21, options)
Search for an interval around 1.21 containing a sign change:
 Func-count    a          f(a)             b          f(b)        Procedure
    1            1.21          -100          1.21          -100   initial interval
    3         1.17578          -100       1.24422          -100   search
    5          1.1616          -100        1.2584          -100   search
    7         1.14155          -100       1.27845          -100   search
    9          1.1132          -100        1.3068          -100   search
   11          1.0731          -100        1.3469          -100   search
   13          1.0164          -100        1.4036          -100   search
Operands to the || and && operators must be convertible to logical scalar values.
Error in fzero (line 365)
        if ~isfinite(fa) || ~isreal(fa) || ~isfinite(a) 
365         if ~isfinite(fa) || ~isreal(fa) || ~isfinite(a)
What is fa now?
K>> whos fa
Name      Size            Bytes  Class     Attributes
fa        1x0                 0  double
fa seems to be empty.
So there are clearly some values of r, such that when your function is called, return an empty result.
Again, while I am still in the debugger, look at a
a
a =
         0.936208254324569
K>> trapecios(a)
ans =
  1×0 empty double row vector
When I pass that number into your function, I get an empty result. Why does that happen? THINK!!!!!
part = 1e-3;
L = 1:part:r;
r is less than 1. What is the vector
1:0.001:.93
ans =
  1×0 empty double row vector
So you need to learn to use the debugger.
How do you fix it? You could recognize that fzero allows you to pass in TWO numbers. That will allow you to bound the lower limit above 1. The problem is then fzero will insist that the two limits to bracket a root.
So simpler as a fix is to put a patch into your objective. At the very beginning of the code, add this:
if r <= 1
  Int = 0;
  return
end
Related Question