Per the docs, "on a typical R platform the smallest positive double is about 5e-324." Given a double vector with values above, near, and below this limit:
library(tibble)
small_vec <- c(4e-300, 4e-324, 4e-350)
small_df <- data.frame(x = small_vec)
small_tibble <- tibble(x = small_vec)
Printing small_vec and small_df give about what I'd expect:
small_vec
#> [1] 4.000000e-300 4.940656e-324 0.000000e+00
small_df
#> x
#> 1 4.000000e-300
#> 2 4.940656e-324
#> 3 0.000000e+00
The second value isn't quite right, which I vaguely understand is due to floating point weirdness. The third number underflows to 0. Fine. But printing as a tibble,
small_tibble
#> # A tibble: 3 × 1
#> x
#> <dbl>
#> 1 4 e-300
#> 2 Inf.e-324
#> 3 0
Created on 2022-10-19 with reprex v2.0.2
I'm thrown by Inf.e-324 -- both the idea of Inf with an exponent, and the decimal point. What does this signify? Or is it possibly a bug in the tibble package?
(A little long for a comment.)
Sure seems like a bug, but I think it's not in tibble per se, but in the pillar package underneath. library(pillar); pillar_shaft(small_vec) shows the same pathology. Digging down: looking at pillar:::format.pillar_shaft_decimal(), it uses the $sci component of this object. That component looks fishy:
> pillar_shaft(small_vec)$sci
[harmless-looking stuff]
$lhs
[1] "4" "Inf" "0"
$lhs_zero
[1] FALSE FALSE TRUE
$rhs
[1] 0 NaN 0
[harmless-looking stuff]
So we probably have to see what pillar_shaft is doing during the conversion.
Specifically in
pillar:::pillar_shaft_number_attr(small_vec, NULL, NULL)
which goes to pillar_shaft_number which seems to lead to
pillar:::split_decimal(small_vec, sigfig = 3, digits = NULL)
but, weirdly enough, that one looks OK, so I must have lost the plot somewhere.