MATLAB: What will be displayd and why

homework

————————————-
if (x)
    disp('true');
else
    disp('false');
end;
if (~x)
    disp('true');
else
    disp('false');
end;
—————————————-
For the case x=[0 0 0 0]
and for the case x=[0 1 0 1]

Best Answer

This is explained quite clearly in the if documentation: "An expression is true when its result is nonempty and contains only nonzero elements (logical or real numeric). Otherwise, the expression is false."
Which means:
  • [0,0,0,0] is false: all values are zero
  • [0,1,0,1] is false: some values are zero
  • ~[0,0,0,0]=[1,1,1,1] is true: contains only nonzero elements
  • ~[0,1,0,1]=[1,0,1,0] is false: some values are zero
Note that the definition defines a true expression as "contains only nonzero elements" but does not give an upper-limit to the number of nonzero elements.
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