[R] The "less than" (<) operator doesnt seem to perform as expected

[R. Michael Weylandt]

It's likely an infelicity of floating point representations (R FAQ
7.31) but admittedly, not a case I would have expected to present
itself.

If you want it to work out as expected, try this:

l <- 0.6
u <- seq(0.4, 0.7, 0.1)

l.int <- (6L) / 10
u.int <- seq(4, 7) / 10

l < u
l.int < u.int

Michael

On Thu, Feb 2, 2012 at 5:00 AM, Jonas Hal <JOH at brf.dk> wrote:
> The example here puzzles me. It seems like the < operator doesn't work as expected.
>
>> l <- 0.6
>> u <- seq(0.4, 0.7, 0.1)
>> u
> [1] 0.4 0.5 0.6 0.7
>> mygrid <- expand.grid("l" = l, "u" = u)
>> mygrid
>    l   u
> 1 0.6 0.4
> 2 0.6 0.5
> 3 0.6 0.6
> 4 0.6 0.7
>> mygridcollapsed <- mygrid[mygrid$l < mygrid$u, ]
>> mygridcollapsed
>    l   u
> 3 0.6 0.6
> 4 0.6 0.7
>
> In this little example I expect 'mygridcollapsed' only to return row 4 and for it to return row 3 seems wrong. The strange thing is it seems to work if I start the u-sequence at 0.5.
>
>> l <- 0.6
>> u <- seq(0.5, 0.7, 0.1)
>> u
> [1] 0.5 0.6 0.7
>> mygrid <- expand.grid("l" = l, "u" = u)
>> mygrid
>    l   u
> 1 0.6 0.5
> 2 0.6 0.6
> 3 0.6 0.7
>> mygridcollapsed <- mygrid[mygrid$l < mygrid$u, ]
>> mygridcollapsed
>    l   u
> 3 0.6 0.7
>
> Maybe I'm missing something...
>
> Best wishes
> Jonas Hal
>
>
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