control over < > for print.tbl_df method

[edzer]

The standard way to print units of measure is between square brackets, as in [km/h]. When I do this in a tibble header, I get <[km/h]>, which looks odd (example below) and takes unnecessary space. Is there a way to get rid of the < and >? Should I raise this issue with tibble?

suppressPackageStartupMessages(library(units))
mt = mtcars
mt$mpg = set_units(mt$mpg, km/h)
library(tibble)
(m <- as.tibble(mt))
# # A tibble: 32 x 11
#         mpg   cyl  disp    hp  drat    wt  qsec    vs    am  gear  carb
#  * <[km/h]> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
#  1     21.0  6.00   160 110    3.90  2.62  16.5  0     1.00  4.00  4.00
#  2     21.0  6.00   160 110    3.90  2.88  17.0  0     1.00  4.00  4.00
#  3     22.8  4.00   108  93.0  3.85  2.32  18.6  1.00  1.00  4.00  1.00
#  4     21.4  6.00   258 110    3.08  3.22  19.4  1.00  0     3.00  1.00
#  5     18.7  8.00   360 175    3.15  3.44  17.0  0     0     3.00  2.00
#  6     18.1  6.00   225 105    2.76  3.46  20.2  1.00  0     3.00  1.00
#  7     14.3  8.00   360 245    3.21  3.57  15.8  0     0     3.00  4.00
#  8     24.4  4.00   147  62.0  3.69  3.19  20.0  1.00  0     4.00  2.00
#  9     22.8  4.00   141  95.0  3.92  3.15  22.9  1.00  0     4.00  2.00
# 10     19.2  6.00   168 123    3.92  3.44  18.3  1.00  0     4.00  4.00
# # ... with 22 more rows

[hadley]

You can define your own type_sum() method, but the <> are added by pillar in order to force the display to be consistent.

[edzer]

A fully unit-ized mtcars generated by

suppressPackageStartupMessages(library(dplyr))
suppressPackageStartupMessages(library(units))
library(tibble)
options(width = 100)
mtcars %>%
	mutate(mpg = set_units(mpg, mile/gallon),
	cyl = set_units(cyl),
	disp = set_units(disp, `in`^3),
	hp = set_units(hp, hp),
	drat = set_units(drat),
	wt = set_units(wt, klb),
	qsec = set_units(qsec, s),
	vs = set_units(vs, V/S),
	am = c("aut", "man")[am+1],
	gear = set_units(gear),
	carb = set_units(carb)
	) %>% 
	as.tibble %>%
	print(width = 100)

now looks like this:

which is nice! However, the < and > pairs are verbose, distracting, and take unnecessary space. Maybe give an optional parameter to type_sum to remove them?

[hadley]

In this case, it seems a bit duplicative to have the type in the heading and next to every individual value.

[edzer]

I agree; I was thinking of making that configurable, and possibly off by default. If left away, the space taken by < and > becomes proportionally more disturbing.

[hadley]

I wonder if it's worth never applying the <> - colour + italics might be sufficient (although then it would have to display differently if colour not available, which is somewhat undesirable)

[edzer]

(I updated my comment above to show the output without units behind each value)

[krlmlr]

I wonder if we could parse the value returned by type_sum(): If it already has parentheses (like {} or [] or <>), we use them. If the value is surrounded by a pair of spaces, we don't add angle brackets.

• "chr" -> "<chr>"
• "[km/h]" -> "[km/h]"
• " Column label " -> "Column label"

In strengejacke/sjlabelled#3 (comment) I was suggesting a

custom column header. We don't have callbacks for this in pillar yet, but I'm happy to provide them. Same idea, but you're overriding a different method. This gives support for multiline headers and even more flexibility, e.g., we could support indicating a minimum width for the data, or word wrapping.

But I'm no longer sure how useful a custom multiline column header would be, given the very limited space available in a terminal.

[krlmlr]

@edzer @etiennebr: Did we discuss that an attribute in the value returned by a type_sum() method could take care of controlling the brackets, and if it's missing, we use the default "<" and ">"?

[etiennebr]

Yes, we discussed it. If I remember correctly we discussed making something like format_full_type generic so it could be called per class (would need a class for labels, I guess) and offer more styling control for each class. But looking at it now, it doesn't seem like the simplest solution.

[krlmlr]

Thanks for the reminder, the new format_type_sum() generic still feels like the right way. Are the examples useful?

CC @strengejacke.

[edzer]

This works without brackets, but it seems to break if I specify square brackets in the type_sum, as in

type_sum.units <- function(x, ...) {
  structure(paste0("[", as.character(units(x)), "]"), class = "type_sum_units")
}

In this case, the last two characters are bitten off.

[edzer]

library(pillar)
type_sum.accel <- function(x) {
  structure("kg m/s^2", class = "type_sum_accel")
}

format_type_sum.type_sum_accel <- function(x) {
  style_subtle(x)
}

accel <- structure(9.81, class = "accel")

pillar(accel)
#> kg m/s  
#> 9.81

Created on 2018-07-14 by the reprex package (v0.2.0).

[krlmlr]

Thanks for the heads-up, I'll work on a fix.

[krlmlr]

What's a good way to turn your output into runnable code? reprex::reprex_rescue() or reprex::reprex_clean() didn't work for me, I edited by hand (and updated your code). It would have been easier if this example was created with reprex::reprex(), which is on CRAN (again).

[krlmlr]

🤦‍♂️🤦‍♂️ It's just the example for format_type_sum()...

[edzer]

Thanks a lot, @krlmlr!

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