fundamental multiplication problems with Matlab2010-2011!!!!
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Dear all!
today I discover something very very very stupid in Matlab.0 This is the code I wrote:
x =
8.4600
>> y=x*10000
y =
8.4600e+004
>> y-84600
ans =
1.4552e-011
HOW THIS IS POSSIBLE????? it's only a multiplication!
3 Comments
Jan
on 30 Aug 2012
@gringorie: You are in a good company - otherwise this topic would be discussed in the "seldom asked questions". Reading the FAQ is a good idea for all software you use, because it is worth to profit from the problems of others.
Accepted Answer
gringoire
on 30 Aug 2012
4 Comments
Sean de Wolski
on 30 Aug 2012
Yes. It means you can't use ismember to get reliable results with floating points.
For the most part when there is something common like this you will have no reason to reinvent the wheel:
More Answers (1)
James Tursa
on 31 Aug 2012
For educational purposes:
>> x = 8.46
x =
8.4600
>> num2strexact(x)
ans =
8.46000000000000085265128291212022304534912109375
>> y = x * 10000
y =
8.4600e+004
>> num2strexact(y)
ans =
8.4600000000000014551915228366851806640625e4
>> y - 84600
ans =
1.4552e-011
>> num2strexact(ans)
ans =
1.4551915228366851806640625e-11
You can find num2strexact here:
href = ""<http://www.mathworks.com/matlabcentral/fileexchange/22239-num2strexact-exact-version-of-num2str</a>>
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