Why get i this result?

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Said BOUREZG 2017-4-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/336326-why-get-i-this-result

关闭： MATLAB Answer Bot 2021-8-20

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 >> a = [10035.99];
>> k=[100 50 20 10 5 2 1 0.5 0.25 0.1 0.05 0.01];
% i must get b=[100 0 1 1 1 0 0 1 1 2 0 4] but ...see the end. 
for i=1:length(k)
     b(i)=fix(a/k(i))
     a=mod(a,k(i))
     end
b =
   100
a =
   35.9900
b =
   100     0
a =
   35.9900
b =
   100     0     1
a =
   15.9900
b =
   100     0     1     1
a =
    5.9900
b =
   100     0     1     1     1
a =
    0.9900
b =
   100     0     1     1     1     0
a =
    0.9900
b =
   100     0     1     1     1     0     0
a =
    0.9900
b =
   100     0     1     1     1     0     0     1
a =
    0.4900
b =
   100     0     1     1     1     0     0     1     1
a =
    0.2400
b =
   100     0     1     1     1     0     0     1     1     2
a =
    0.0400
b =
   100     0     1     1     1     0     0     1     1     2     0
a =
    0.0400
b =
   100     0     1     1     1     0     0     1     1     2     0     3
a =
    0.0100

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John D'Errico 2017-4-20

The 1 million'th person to ask this, or an equivalent question.

http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

Stephen23 2017-4-20

This is such a common topic that it has been discussed thousands of times before. Try searching this forum for "floating point equals", or start by reading these:

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

https://www.mathworks.com/matlabcentral/answers/316889-why-two-equal-numbers-are-not-equal

http://www.mathworks.com/matlabcentral/answers/102419-how-do-i-determine-if-the-error-in-my-answer-is-the-result-of-round-off-error-or-a-bug

http://www.mathworks.com/matlabcentral/answers/140656-about-numerical-difficulty-of-equality-comparison-operation-between-two-double-real-numbers-in-matlab

This is worth reading as well:

https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

http://faculty.tarleton.edu/agapie/documents/cs_343_arch/papers/1991_Goldberg_FloatingPoint.pdf

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