Prompt users about pillar::num() for customising the rounding of numbers

[charliejhadley]

The {pillar} package has recently introduced num() to aid in customising how {tibble} prints rounded numbers.

There have been a few issues requesting this feature, I originally opened r-lib/pillar#97 which includes both a reprex and suggested fix r-lib/pillar#97 (comment)

It's difficult to tell {pillar} not to round numbers straddling 0 - 1

library("tidyverse")
#> ── Attaching packages ──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── tidyverse 1.2.1 ──
#> ✔ ggplot2 2.2.1     ✔ purrr   0.2.4
#> ✔ tibble  1.4.2     ✔ dplyr   0.7.4
#> ✔ tidyr   0.8.0     ✔ stringr 1.2.0
#> ✔ readr   1.1.1     ✔ forcats 0.2.0
#> ── Conflicts ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── tidyverse_conflicts() ──
#> ✖ dplyr::filter() masks stats::filter()
#> ✖ dplyr::lag()    masks stats::lag()
my_numbers <-  c(233, 486, 565, 785)
straddle_data <- tibble(
  big = 1000 * my_numbers + 23,
  stradle = my_numbers / 1000 + 100,
  small = my_numbers / 100000
)
straddle_data
#> # A tibble: 4 x 3
#>      big straddle   small
#>    <dbl>   <dbl>   <dbl>
#> 1 233023     100 0.00233
#> 2 486023     100 0.00486
#> 3 565023     101 0.00565
#> 4 785023     101 0.00785

Which is now controllable with

library(pillar)

extra_digits <- function(x) {
  x <- sort(abs(x))
  delta <- diff(x)
  x <- x[-1]

  keep <- which((delta != 0) & is.finite(delta))
  if (length(keep) == 0) {
    return(0)
  }

  x <- x[keep]
  delta <- delta[keep]

  ceiling(log10(max(x / delta)))
}

num_with_extra_digits <- function(x) {
  num(x, sigfig = 3 + extra_digits(x))
}

my_numbers <- c(233, 486, 565, 785)

tibble::tibble(
  big = num_with_extra_digits(1000 * my_numbers + 23),
  straddle = num_with_extra_digits(my_numbers / 1000 + 100),
  straddle2 = num_with_extra_digits(my_numbers / 1000 + 1000),
  straddle3 = num_with_extra_digits(my_numbers / 10000 + 10000),
  small = num_with_extra_digits(my_numbers / 100000)
)
#> # A tibble: 4 × 5
#>       big straddle straddle2  straddle3   small
#>   <num:4>  <num:7>   <num:8>   <num:10> <num:4>
#> 1  233023  100.233  1000.233 10000.0233 0.00233
#> 2  486023  100.486  1000.486 10000.0486 0.00486
#> 3  565023  100.565  1000.565 10000.0565 0.00565
#> 4  785023  100.785  1000.785 10000.0785 0.00785

---

I feel it would be useful for {tibble} to make users aware of the num() functionality.

Would it be possible to print a message to users on a once per session basis, specifically if {pillar} trims a number like 100.233 to 100. ?

[krlmlr]

This will soon be even easier in pillar. I'm not sure about a startup message, perhaps we can add more links to the documentation to make this particular formatting options easier to discover?

[krlmlr]

With pillar 1.6.2:

library(tibble)
packageVersion("pillar")
#> [1] '1.6.2'

my_numbers <- c(233, 486, 565, 785)

tibble::tibble(
  big = num(1000 * my_numbers + 23, extra_sigfig = TRUE),
  straddle = num(my_numbers / 1000 + 100, extra_sigfig = TRUE),
  straddle2 = num(my_numbers / 1000 + 1000, extra_sigfig = TRUE),
  straddle3 = num(my_numbers / 10000 + 10000, extra_sigfig = TRUE),
  small = num(my_numbers / 100000, extra_sigfig = TRUE)
)
#> # A tibble: 4 × 5
#>      big straddle straddle2  straddle3   small
#>    <num>    <num>     <num>      <num>   <num>
#> 1 233023  100.233  1000.233 10000.0233 0.00233
#> 2 486023  100.486  1000.486 10000.0486 0.00486
#> 3 565023  100.565  1000.565 10000.0565 0.00565
#> 4 785023  100.785  1000.785 10000.0785 0.00785

^{Created on 2021-08-01 by the reprex package (v2.0.0.9000)}

Now we have the following path to discover this information:

1. https://tibble.tidyverse.org/dev/index.html (soon without /dev, and from README.md too)
2. vignette("tibble")
3. "Tibbles vs. data frames" section, "Printing" subsection
4. vignette("digits", package = "pillar") in "See also" in that section

From there on it becomes a bit fuzzy. Some information is in vignette("numbers"), but there's no link. Now that num() is reexported in tibble, maybe we can duplicate the documentation in ?num and vignette("digits") here and also brush up vignette("digits")? Do we still need the startup message? Curious to hear your thoughts.

[krlmlr]

Action items:

• Move vignettes("digits") and vignettes("numbers") here
• Move num() and char() documentation here
• Clean up and enhance numbers vignette
• Mention new extra_sigfig
• Add cross-references
• Clean up in pillar: relink digits vignette, shorten numbers vignette, replace ?num, ?char and print.tbl() with internal stubs
• Revisit

[github-actions]

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