CODEWITHSUNDEEP
matlabrounding
Johnny5
Johnny5

Reputation: 6852

MatLab - 9.45 representation and round

>> a = 12.5 * 9.45

a =

     1.181250000000000e+02

>> round(a * 100) /100

ans =

     1.181200000000000e+02

The rounded value should be 118.13, not 118.12.

If you type 9.45 in MatLab command line, it can't be represented : 

>> 9.45

ans =

   9.449999999999999

If I set the numeric format to short, the final result is the same.

>> a = 12.5 * 9.45

a =

  118.1250

>> round(a * 100) / 100

ans =

  118.1200

Can someone explain that? Any workaround?

Upvotes: 0

Views: 144

Answers (2)

grantnz
grantnz

Reputation: 7423

You could try something like John D'Errico's hpf class.

This will give the result you are expecting

round(hpf('12.5') * hpf('9.45') * 100)/100
ans =
118.13


F = hpf('9.45')
F =
9.45

Upvotes: 3

NominSim
NominSim

Reputation: 8511

Sounds like you've got some settings that are messing with your output precision. It looks like your current settings want 15 decimal places(possibly longG)?, and with MATLABs floating point numbers you won't get 100% precision that far.

You can change the format of your display output, but the precision is going to be an issue to that level regardless. The relevant documentation.

Upvotes: 0

Related Questions