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Why the result of (1-0.6667)==0.3333 is zero in MATLAB? how can I get one?

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may
may 2013-2-26
Why the result of (1-0.6667)==0.3333 is zero in MATLAB? how can I get one?
when I use matlab to calculate 1-0.6667 I get 0.3333. but the result of (1-0.6667)==0.3333 is zero I even tried this one
t=1-0.6667;
t==0.3333
the result is again 0.
how can I get one for (1-0.6667)==0.3333?

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回答（6 个）

Azzi Abdelmalek
Azzi Abdelmalek 2013-2-26
编辑：Azzi Abdelmalek 2013-2-26
Because 0.6667 and 0.3333 are codified and stored in the memory with a certain precision
per isakson
per isakson 2013-2-26
编辑：per isakson 2013-2-26
Shashank Prasanna
Shashank Prasanna 2013-2-26
That is because they are not the same.
>> t-0.3333
ans =
5.55111512312578e-17
They can be equal by some tolerance.
>> t-0.3333 < 1e-15
ans =
1
Youssef Khmou
Youssef Khmou 2013-2-26
hi may,
This precision problem, so your numbers are 4 decimals , i suggest to make to make your logical test by multiplying your numbers by 1E+4 :
a=0.6667;
b=0.3333;
f=1e+4; % Factor
f-f*a==f*b % ITS NOT f*(1-a)==f*b
Jan
Jan 2013-2-27
This is the most frequently asked question. See FAQ: why is 0.3-0.2~=0.1
Matt J
Matt J 2013-2-26
编辑：Matt J 2013-2-26
Why the result of (1-0.6667)==0.3333 is zero in MATLAB? how can I get one?
The others have told you why. You can get "one", however, by reformulating this way,
>> (3-2)/3==1/3
ans =
1

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