MATLAB: Undefined variable “U”

MATLAB

E = [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0];
E1 = [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0];
e = 1;
E(1) = U{1}(1);
e = e + 1;
e1 = 1;
E1(1) = U{1}(2);
e1 = e1 + 1;
for i = 1:numel(U)
   a = U{i};
   for t = 1:numel(E)
       if a(1) == E(t);
           E1(e1) = a(2);
           e1 = e1 + 1;
       else if a(2) == E(t);
           E1(e1) = a(1);
           e1 = e1 + 1;
            end
       end
   end
help pls how can i define it

Best Answer

Let me guess, what your question might mean: The message
 Undefined variable "U"
is shown, when you try to run this line:
E(1) = U{1}(1);
Then the message is clear: The variable "U" is not existing yet. The posted piece of code does not clarify where this variable might be coming from.
Speculation: Perhaps you have defined U in the inputs, but started the function using the "Start" button (the green triangle). This cannot work, because the input must be provided to define U.
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