Elements From a Matrix A bit Off

I am a new user of Matlab and I am sure there must be a good reason for this. Here are the code and output: >> a=[0:0.1:0.5]; >> b=0.5-a; >> [a(2) b(5)]

ans =

          0.1          0.1

The two numbers look the same in this case. However, when I checked: >> a(2)==b(5)

ans =

     0
And

>> a(2)-b(5)

ans =

2.7756e-017

They are actually slightly off. Does anyone know why?

Also, how can I prevent the unwanted consequences from using elements from the matrix, i.e. b(5) is actually not exactly 0.1? Right now, I am just rounding it, which woudl be a bit annoying from time to time. Hope there are better ways to do this.

Cheers!

Fred

Answer 1

[Azzi Abdelmalek]

Look at http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F