Trapz abnormal behavior. Error:Subscript indices must either be real positive integers or logicals.

When I enter:

>> trapz(2,2)

ans =

       0

When I enter:

>> trapz(2.2,2.2)

Subscript indices must either be real positive integers
or logicals.

Error in ipermute (line 23)
inverseorder(order) = 1:numel(order);   % Inverse
permutation order

Error in trapz (line 73)
if ~isempty(perm), z = ipermute(z,perm); end

Why trapz is having trouble in such case?

Answer 1

[Azzi Abdelmalek]

What are you expecting with trapz(2.2,2.2)? to compute the integral along x, you will need at least 2 points

[Giorgos Papakonstantinou]

trapz(2,2) which yields 0 is two points?. The numerical integral should be zero. So I expect 0. If that was the case then it should fail also at trapz(2,2).

[Azzi Abdelmalek]

%(2,2) is one point with x=2 and y=2.
% tarpz(2,2) returns 0, but I'm not sure if it's computing an integral, even the expected result is 0.

Answer 2

[Walter Roberson]

When you use trapz() and the second argument is a scalar, then you are invoking the behavior trapz(Y,DIM) where DIM is to be a dimension number, which must be a positive integer.