Message-ID: <42492CDA.5040501@mpiib-berlin.mpg.de>
Date: 2005-03-29T10:24:26Z
From: Klaus-Peter Pleissner
Subject: strange result of acos
Hi all,
I have to calculate an expression using acos -function. A strange
result of acos appears
*1. case with error*
ss <- sin(10.74*pi/180)**2
+(cos(10.74*pi/180)*cos(10.74*pi/180)*cos(0*pi/180))
ss
acos(ss)
[1] NaN
Warning message:
NaNs produced in: acos(ss)
*2. case without error*
ss <- sin(10.7*pi/180)**2
+(cos(10.7*pi/180)*cos(10.7*pi/180)*cos(0*pi/180))
ss
acos(ss)
In both cases the variable ss equals 1. I think there is a problem
with precision. If I multiply ss by 0.999999999 (ss*0.99999999) no
error occurs. How the results can be explained ?
Regards
Klaus-P.
--
Dr. Klaus-Peter Pleissner
Max Planck Institute for Infection Biology
Core Facility Bioinformatics
Campus Charit? Mitte
Schumannstr. 21/22
D-10117 Berlin
Germany
*Phone:* +49-30-28460-119
*Fax:* +49-30-28460-507
*URL:* http://web.mpiib-berlin.mpg.de/bioinformatik <http://web.mpiib-berlin.mpg.de/bioinformatik/>
*Email:* pleissner at mpiib-berlin.mpg.de <mailto:pleissner at mpiib-berlin.mpg.de>