Comparing double precision numbers

Two and a half minute video covers the tolerances in double precision numbers

Description

Sometimes you will do a calculation where the answer looks like '0' or '1' or some other number like that. The natural thing to do is to do a test like this:
                    
if (answer == 1)
     Do something
end
                    
However, if the calculation was done in double precision, answer might actually be 1.000000001 or something like that. This video discusses a strategy for overcoming this:
                    
if abs(answer - 1) < 1e-14
     Do something
end
                    
See more videos without downloading here: http://blogs.mathworks.com/videos/category/video/

• MATLAB release: MATLAB 7.7 (R2008b)
• HTML Files: Video from http://blogs.mathworks.com/pick
• Other Files: 136 Advanced tolerances.flv, ; 136 Advanced tolerances.js, ; 136 Advanced tolerances_config.xml, ; 136 Advanced tolerances_controller.swf, ; 136 Advanced tolerances_nofp_bg.gif, ; 136 Advanced tolerances_preload.swf, ; FlashTemplate.css, ; mCode/main.m, ; ProductionInfo.xml, ; swfobject.js

[Thierry Dalon]

The video contains not much more than the description.

See also function EPS.