Significant figures and scientific notation

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
library(pillar)

Base R offers the "digits" and "scipen" options to control the number of significant digits and the switch to scientific notation. For pillar, the options "pillar.sigfig" and "pillar.max_dec_width" fulfill a similar purpose. This vignette showcases similarities and differences. See ?"pillar-package" for an overview over all options.

Digits

Basic differences

The default for getOption("digits") is 7, whereas the "pillar.sigfig" option defaults to 3. In the default setting, pillar prints the first three digits only (i.e. the digits that represent > 99.9% of the value of the number). Another difference is that pillar will show at most the specified number of significant digits, even if space is available. The rationale is to allow a quick glance over the most significant digits of a number, without spending too much horizontal space and without distraction from insignificant digits.

options(digits = 3)
c(1.2345, 12.345, 123.45, 1234.5, 12345)
pillar(c(1.2345, 12.345, 123.45, 1234.5, 12345))

Terminal zeros

Terminal zeros are only shown in pillar if there is a nonzero value past the significant digits shown. This is in contrast to base R where terminal zeros are always shown if there is space, but hidden if the value is too insignificant:

c(1, 1.00001)
pillar(c(1, 1.00001))

Trailing dot

A trailing decimal separator is shown if there is a fractional part but the integer part already exceeds the significant digits. The presence of the decimal separator does not indicate that the number is larger, only that there exists a nonzero fractional part:

c(123, 123.45, 567.89)
pillar(c(123, 123.45, 567.89))

Showing more digits

To show more significant digits, set the "pillar.sigfig" option to a larger value:

options(digits = 7)
options(pillar.sigfig = 7)
c(1.2345, 12.345, 123.45, 1234.5, 12345)
pillar(c(1.2345, 12.345, 123.45, 1234.5, 12345))

Setting "pillar.sigfig" to a larger value will not enhance the display with digits deemed insignificant:

options(digits = 7)
options(pillar.sigfig = 7)
c(1.2345, 12.3456, 123.4567, 1234.5678, 12345.6789)
pillar(c(1.2345, 12.3456, 123.4567, 1234.5678, 12345.6789))

Fixed number of digits

To show a fixed number of decimal digits, use num() with a digits argument:

num(c(1.2345, 12.345, 123.45, 1234.5, 12345), digits = 2)

See vignette("numbers") for details.

Scientific notation

When is it used?

Both base R and pillar switch to scientific notation when the decimal representation becomes too wide. The larger getOption("scipen"), the stronger the resistance to switching to scientific notation. The default 0 seems to be anchored at 13 digits for the integer part.

123456789012
123456789012.3
1234567890123
1234567890123.4
options(scipen = 1)
1234567890123
12345678901234
12345678901234.5

The "pillar.max_dec_width" option is similar, it indicates the width that must be exceeded for a switch to scientific notation to happen. This width includes the decimal separator.

pillar(123456789012)
pillar(123456789012.3)
pillar(1234567890123)
pillar(1234567890123.4)
options(pillar.max_dec_width = 14)
pillar(1234567890123)
pillar(12345678901234)
pillar(12345678901234.5)

Enforce notation

To avoid switching to scientific notation, set the "pillar.max_dec_width" option to a large value. Note that if the required width is not available to show the column, it will not be shown at all in this case. The notation argument to num() offers more options:

num(12345678901234567, notation = "dec")
num(12345678901234567, notation = "sci")
num(12345678901234567, notation = "eng")
num(12345678901234567, notation = "si")


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pillar documentation built on July 29, 2021, 9:06 a.m.