error (rounding or user) in simple math op

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Jason
Jason 2013-1-8
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)

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采纳的回答

Azzi Abdelmalek
Azzi Abdelmalek 2013-1-8
编辑：Azzi Abdelmalek 2013-1-8
Use
format short
The problem is simply caused by the way, real data are stored in memory

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José-Luis
José-Luis 2013-1-8
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José-Luis
José-Luis 2013-1-9
Please accept an answer if it helped you.
Jan
Jan 2013-1-9
编辑：Jan 2013-1-9
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".

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