RE: Comparing of values

[Hall, Benjamin]

Searching for exact matches to floating point numbers can be troublesome
just due to the nature of floating point numbers in computers
(unfortunately, I can't really give a better answer than that!).  For
instance

>> 3*0.05 - 0.15

ans =

  2.7756e-017

One work-around is the following:

beta = 0.05:0.05:0.95;

beta( beta == 3*0.05 )

or

beta( abs( beta - 0.15 ) < 0.00000001 ) 

Hope that helps 


-----Original Message-----
From: Jakub Selesovsky [mailto:address@hidden
Sent: Friday, October 22, 2004 9:40 AM
To: address@hidden
Subject: Comparing of values


Hello,

I have a problem with searching of values in vector. What is wrong in  
following sequence of commands? I mean why Octave (2.1.50, Linux, compiled  
 from source) return some values when searching beta==0.05, and return zero

vector when searching beta==0.15. Both of these values are included in  
vector beta. Thank you for each answer.

Jakub Selesovsky

octave:10> beta = rot90(0.05:0.05:0.95,-1)
beta =

   0.050000
   0.100000
   0.150000
   0.200000
   0.250000
   0.300000
   0.350000
   0.400000
   0.450000
   0.500000
   0.550000
   0.600000
   0.650000
   0.700000
   0.750000
   0.800000
   0.850000
   0.900000
   0.950000

octave:11> beta = [beta; beta; beta; beta; beta]
octave:12> beta(beta==0.15)
ans = [](0x1)
octave:13> beta(beta==0.05)
ans =

   0.050000
   0.050000
   0.050000
   0.050000
   0.050000

octave:14>




-- 
Jakub Selesovsky
--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/



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Octave is freely available under the terms of the GNU GPL.

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