error (rounding or user) in simple math op

I just noticed odd behavior in R2012b that really seems like an error though perhaps I'm making a foolish error?

I enter the following >> 2.7+1.8*[1,2,3,4,5,6,7,8,9]

I expect 4.5 6.3 8.1 9.9 11.7 13.5 15.3 17.1 18.9

I get: ans =

Columns 1 through 5

   4.500000000000000   6.300000000000001   8.100000000000001  9.900000000000000  11.699999999999999

Columns 6 through 9

   13.500000000000000  15.300000000000001  17.100000000000001  18.899999999999999

This seems odd to me for obvious reasons. Even something simple like

>> 1.8*9

ans =

16.199999999999999

how could this be happening?

Thank you

(p.s. its 8.0.0.783 R2012b)

Answer 1

[Azzi Abdelmalek]

Use

 format short

The problem is simply caused by the way, real data are stored in memory

Answer 2

[José-Luis]

It is due to numerical precision, and is expected behavior.

http://www.mathworks.com/matlabcentral/answers/57444-faq-why-is-0-3-0-2-0-1-not-equal-to-zero

[Jason]

I expect 0 not to always be 0 but this is a bit much:

1.1*9999 ans = 1.099890000000000e+04

The result is off by 0.1

[Jason]

doh, never mind.

[José-Luis]

That's just a matter of how you are displaying the number. Please try format long as Azzi suggests. The number should then be displayed with all its precision.

[José-Luis]

Please accept an answer if it helped you.

[Jan]

This could be more helpful here:

format long g

But what is wrong with "1.1*9999 ans = 1.099890000000000e+04"? 1.1*9999 is 10998.9 or 1.09989e4. I cannot see why this should be "off by 0.1".