MATLAB: About the calculation precise

calculationprecise

The precise of calculation has a problem when I add 60.425 with 0.425. The exact value should be 60.85, however I just got 60.8499999…, which affects my following calculation. How I can avoid such problem?

Best Answer

http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

Related Solutions

MATLAB: Rounding using ‘fix’… possibly a bug

To see what is going on you can examine the exact floating point values. Note that none of your original numbers except 0.5 can be represented in IEEE double format exactly:

>> num2strexact(.7)
ans =
0.6999999999999999555910790149937383830547332763671875
>> num2strexact(.5)
ans =
0.5
>> num2strexact(.4)
ans =
0.40000000000000002220446049250313080847263336181640625
>> num2strexact(.3)
ans =
0.299999999999999988897769753748434595763683319091796875
>> num2strexact(.1)
ans =
0.1000000000000000055511151231257827021181583404541015625
>> num2strexact(.7/.1)
ans =
6.99999999999999911182158029987476766109466552734375
>> num2strexact(.5/.1)
ans =
5
>> num2strexact(.4/.1)
ans =
4
>> num2strexact(.3/.1)
ans =
2.999999999999999555910790149937383830547332763671875

You can find num2strexact here:

http://www.mathworks.com/matlabcentral/fileexchange/22239-num2strexact-exact-version-of-num2str

MATLAB: 0.9-0.89 is 0.010000000000000000208166817117217

One of the most frequently asked questions, so see the FAQ: http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

Best Answer

Related Solutions

MATLAB: Rounding using ‘fix’… possibly a bug

MATLAB: 0.9-0.89 is 0.01000000​0000000000​2081668171​17217

Related Question

MATLAB: 0.9-0.89 is 0.010000000000000000208166817117217