scales::breaks_pretty()

Sarah Gothard

In this document, I will introduce the breaks_pretty() function and show what it’s for.

library(tidyverse)

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library(palmerpenguins)

## Warning: package 'palmerpenguins' was built under R version 4.0.3

library(scales)

## Warning: package 'scales' was built under R version 4.0.3

## 
## Attaching package: 'scales'

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data(penguins)

The “breaks_pretty” function is used to find best fit “breaks” or intervals in a data set.

#creating simple breaks in a month
one_month <- as.POSIXct(c("2020-05-01", "2020-06-01"))
demo_datetime(one_month, breaks = breaks_pretty(2))

## scale_x_datetime(breaks = breaks_pretty(2))

demo_datetime(one_month, breaks = breaks_pretty(4))

## scale_x_datetime(breaks = breaks_pretty(4))

#more complex breaks and/or data sets will sometimes lead to greater or fewer intervals than desgnated by your "n" because the breaks_pretty package intuitively finds breaks near your desired number of intervals that fits the data assigned best.

demo_datetime(one_month, breaks = breaks_pretty(12))

## scale_x_datetime(breaks = breaks_pretty(12))

#output has more than 12 breaks

Funciton Discussion and Use

Breaks_pretty is found in the “scales” package and takes advantage of an existing r package/algorithm, “pretty()”. In practice, breaks_pretty() is most commonly used to designate the tics/intervals of dates/times/continuous variables in ggplot visualizations.

#when using breaks_pretty() add you can either designate your argument's n explicity, (n = 6) or it defaults to that as the first argument and pass in just the number of breaks you'd like to see (6).

ggplot(penguins,
       aes(x = bill_length_mm,
           y = body_mass_g)) +
  geom_point() +
  geom_smooth() +
  scale_x_continuous(name = "Bill Length (mm)",
                     breaks = breaks_pretty(6)) +     # breaks_pretty
  scale_y_continuous(name = "Body Mass (g)",
                     breaks = breaks_pretty(n = 8)) +
  theme_light()

## `geom_smooth()` using method = 'loess' and formula 'y ~ x'

## Warning: Removed 2 rows containing non-finite values (stat_smooth).

## Warning: Removed 2 rows containing missing values (geom_point).

Is it helpful?

Breaks_pretty is very useful as it simplifies how we desginate intervals (tics) in our ggplots. Instead of hardcoding the intervals we want to see, breaks_pretty intuitively designates tics close to our desired widths.