[datatable-help] sorting on floating point column

[Arunkumar Srinivasan]

Hi there, 

I just saw something strange when I was sorting a column of p-values. I checked the data.table bug tracker for words "sort" and "floating point" and there were no hits for this case. There's a bug for "integer 64" sort on a column though.

So, here's a reproducible example. I'd be glad to file a bug, if it is and be corrected if it's something I am doing wrong.

set.seed(45)
dt <- data.table(x=sample(50), y= sample(c(seq(0, 1, length.out=1000), 7000000:7000100), 50)/1e7)
head(dt)
    x            y
1: 32 5.395395e-08
2: 16 6.956957e-08
3: 12 2.142142e-08
4: 18 5.855856e-08
5: 17 6.216216e-08
6: 14 5.025025e-08
setkey(dt, "y") # sort by column y
head(dt, 10)
     x            y
 1: 47 1.401401e-09
 2: 12 2.142142e-08
 3: 24 1.391391e-08
 4: 43 9.809810e-09 <~~~ obviously false
 5:  1 2.932933e-08
 6: 48 2.562563e-08
 7: 49 1.891892e-08
 8: 40 2.182182e-08
 9:  9 7.307307e-09 <~~~ obviously false
10: 45 2.482482e-08


Best,
Arun

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