diff() function in R and logical comparisons

Asked Oct 19 '17 at 13:20

Active Oct 19 '17 at 13:32

Viewed 103 times

I almost feel silly asking this question but I'm completely new to R and I just can't seem to figure this out.

For a vector v and v.2

v=c(0,0.9,1,1.1,1.3,2.3,2.8,3.0,5.0,5.9,6.0,8.2,9.8)
v.2=diff(v)
  [1] 0.9 0.1 0.1 0.2 1.0 0.5 0.2 2.0 0.9 0.1 2.2 1.6

I want to find which differences are smaller than 1 i.e. v.2<1

And I get this crazy output:

TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE FALSE  TRUE  TRUE FALSE FALSE

where apparently v.2[5]=1.0, but it's still registered as "true".

Why would this be the case?

asked Oct 19 '17 at 13:20

V.B

2

Have a look at `2.3 - 1.3; 2.3 - 1.3 - 1` – jogo Oct 19 '17 at 13:31
1

`v.2[5] - 1` gives `-2.220446e-16` the problem comes from `R` precision for floating points – Cath Oct 19 '17 at 13:32
1

Thanks so much - I was going a little crazy. – V.B Oct 19 '17 at 13:35

0 Answers0