[R] R rounding problem?

[array chip]

Hello,

I made a mistake today on simple counting in R, that almost got me into trouble. After trying multiple times, I finally figured out it's rounding issue in R.

For exmaple, when I just simply type:

> (6.9-6.3) > 0.6
[1] TRUE

6.9-6.3 should be 0.6 exactly, but R thinks that it's greater than 0.6!!

Similarly, R thinks 5.6-5.5 is smaller than 0.1:

> (5.6-5.5) < 0.1
[1] TRUE

Why is the above happening? This rounding issue seems to be small, but this could cause serious problem in real world.

Can anyone shed a light on how to avoid the issue?

Thanks,

Yi