trailing 01s and 9s

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Leor Greenberger
Leor Greenberger el 20 de Sept. de 2011
Hi guys,
I'm having rounding issues in my answers:
freq_in = 1.499;
h = 0:1:H-1;
f_harm = (h+1)*freq_in
f_harm =
1.499000000000000 2.998000000000000 4.497000000000000 5.996000000000000 7.495000000000001
f_gdf = mod(f_harm,40/8);
f_gdf =
1.499000000000000 2.998000000000000 4.497000000000000 0.996000000000000 2.495000000000001
a = (2*mod((1:I)',2)-1) * f_gdf;
f_gd = repmat((Fs*floor((g+1)/2)/I)',1,H) + a
f_gd =
1.499000000000000 2.998000000000000 4.497000000000000 0.996000000000000 2.495000000000001
3.501000000000000 2.002000000000000 0.503000000000000 4.004000000000000 2.504999999999999
6.499000000000001 7.998000000000000 9.497000000000000 5.996000000000000 7.495000000000001
8.500999999999999 7.002000000000000 5.503000000000000 9.004000000000000 7.504999999999999
11.499000000000001 12.998000000000001 14.497000000000000 10.996000000000000 12.495000000000001
13.500999999999999 12.001999999999999 10.503000000000000 14.004000000000000 12.504999999999999
16.498999999999999 17.998000000000001 19.497000000000000 15.996000000000000 17.495000000000001
18.501000000000001 17.001999999999999 15.503000000000000 19.003999999999998 17.504999999999999
The trailing 9s are causing problems in my script later on when I use the floor function. Is there a method for rounding it to whatever it would take to flip the 9s into 0s? Thanks.

Respuesta aceptada

Jan
Jan el 20 de Sept. de 2011
The numbers are stored in the binary format inside the computer. For the display on the screen they are converted to the decimal format, which leads to the observed effects of trailing ...0001 and ...999. There is simply no "exact" equivalence between binary and decimal representations.
If your program depends on the value of certain digits in the numerical representation, you have to use integer values smaller than 2^53, because they can be repesented exactly. So think of multiplying your data with the needed factor, which might be 1000 in your case.
  1 comentario
Leor Greenberger
Leor Greenberger el 20 de Sept. de 2011
Thanks Jan and Walter. I actually posted a second question on the subject, which might help me clear up this issue.

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Walter Roberson
Walter Roberson el 20 de Sept. de 2011

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