"uniques" giving duplicates... Matlab adding a tiny sum?

When I look for the unique values of P in column 1, i get a duplicated 0.975...

Somewhere along the line, Matlab probably decided to add a 1 x 10^-28 to some of the cells or something!

I want the 0.975's to be the same, so that on a graph & legend, I no longer get duplicated lines.

:-)

Cause?

Solution?

Doron

>> PU = unique(P(:,1))

PU = ... 0.7000 0.8000 0.9000 0.9250 0.9500 0.9750 0.9750 1.0000

Answer 1

[Walter Roberson]

http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

[Doron]

...Not this again!

thanks Walter

[Walter Roberson]

Yup, again ;-) You will get to the point where you don't trust _any_ floating point comparison. Use liberal doses of paranoia in floating point computations.

[Sean de Wolski]

We should sell floating point awareness tin foil hats.

[Walter Roberson]

In some of my earlier incarnations, I had to assume that there might be compiler bugs in the floating point calculations. Not that such bugs were at all *common*, but you wouldn't want to bet someone's safety on the assumption that there were no invisible glitches.