MATLAB: MOD bug? Or something else

faq 6.1no bugnot a bug

Seems to be a bug in MOD. The values inside the range from 0 to 1 that should result in MOD of 0 (or 0 to machine precision) for the example below (i.e., 0.4 and 0.8) are no where near 0.
>> [-2:.2:2;mod(-2:.2:2,.4)]'
ans =
   -2.0000         0
   -1.8000    0.2000
   -1.6000         0
   -1.4000    0.2000
   -1.2000         0
   -1.0000    0.2000
   -0.8000    0.0000
   -0.6000    0.2000
   -0.4000    0.0000
   -0.2000    0.2000
         0         0
    0.2000    0.2000
    0.4000    0.4000
    0.6000    0.2000
    0.8000    0.4000
    1.0000    0.2000
    1.2000         0
    1.4000    0.2000
    1.6000         0
    1.8000    0.2000
    2.0000         0
I am running R2011a on UNIX… anyone else encounter this problem?

Best Answer

Floating point arithmetic.... Look closely at the numbers.
x = [-2:.2:2];
fprintf('%16.16f\n',x)
You can read more about it here.
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