Is this a bug? different results when performing simple math operation (A * (B - C)) with scalars or variables

Hello everybody,

I am performing same operation A * (B - C) two times. First with variables, then with numbers (scalars). I get different results.

I am providing the output from the command window.

Can somebody please help on this issue?

Thank you,

Answer 1

[Walter Roberson]

If you use

format long g

you will see that ptfDur is not exactly the same as the constant 4.5501 . For example, test

ptfDur - 4.5501

and you will see that the result is non-zero.

Working backwards

C1 = 3 - (-134684353.5829 / 86885000)

C1 = 
          4.55014506051562

C2 = 3 - (-134680438.5 / 86885000)

C2 = 
                    4.5501

C1 - C2

ans = 
      4.50605156236961e-05

Your actual value is about 4E-5 larger than was being displayed, because the default format short only displays 4 digits.

[Programmer x.0]

Many thanks :)