Graphical scales map data to aesthetics, and provide methods for automatically determining breaks and labels for axes and legends.
One of the most difficult parts of any graphics package is scaling, converting from data values to perceptual properties. The inverse of scaling, making guides (legends and axes) that can be used to read the graph, is often even harder! The idea of the
scales package is to implement scales in a way that is graphics system agnostic, so that everyone can benefit by pooling knowledge and resources about this tricky topic.
scales package is made up of the following interdependent components
Palettes, pal for short, describe the useful palettes of aesthetics.
Transformations, trans for short, describe common scale transformations, their inverses, and ways of generating breaks and labels.
Bounds: various ways of rescaling the data
Scaling functions: pull together palettes, bounding functions and transformations to provide a complete pathway from raw data to perceptual properties
Mutable ranges: in many graphics pathways, scale ranges can not be computed in a single pass, but must be computed over multiple groups or multiple panels. The mutable ranges (implemented with R's new reference based class) provide a thin layer of mutability to make this task easier.
regular_minor_breaks() calculates minor breaks as a property
of the transformation (@karawoo).
viridis_pal() for creating palettes with color maps from the
viridisLite package (@karawoo).
Switched from reference classes to R6 (#96).
rescale_mid() are now S3 generics, and work with
bit64::integer64 objects (@zeehio, #74).
extended_breaks() no longer fails on pathological inputs
hms_trans() for transforming hms time vectors.
train_discrete() gets a new
na.rm argument which controls whether
NAs are preserved or dropped.
manual_pal() produces a warning if n is greater than the number of values
in the palette (@jrnold, #68).
precision(0) now returns 1, which means
percent(0) now returns 0% (#50).
scale_continuous() uses a more correct check for numeric values.
NaN is correctly recognised as a missing value by the gradient palettes (ggplot2#1482).
rescale() preserves missing values in input when the range of
(effectively) 0 (ggplot2#985).
Continuous colour palettes now use
colour_ramp() instead of
This only supports interpolation in Lab colour space, but is hundreds of
date_format() gains an option to specify time zone (#51).
dollar_format() is now more flexible and can add either prefixes or suffixes
for different currencies (#53). It gains a
to show negative values as
($100) and now passes missing values through
unchanged (#40, @dougmitarotonda).
ordinal_format() generates ordinal numbers (1st, 2nd etc)
unit_format() makes it easier to add units to labels, optionally
scaling (@ThierryO, 46)
wrap_format() function to wrap character vectors to a desired width.
New color scaling functions
col_factor(). These functions provide concise ways to map continuous or
categorical values to color spectra.
colour_ramp() function for performing color interpolation in the CIELAB
color space (like
grDevices::colorRamp(space = 'Lab'), but much faster).
boxcox_trans() returns correct value when p is close to zero (#31).
percent() both correctly return a zero length string
for zero length input (@BrianDiggs, #35)
brewer_pal() gains a
direction argument to easily invert the order
of colours (@jiho, #36).
show_col() has additional options to showcase colors better (@jiho, #52)
Relaxed tolerance in
.Machine$double.eps * 1000 (#33).
Eliminate stringr dependency.
Fix outstanding errors in R CMD check
to_time, but that function was moved into a function
so it was no longer available in the scales namespace. Now
has its own copy of that function. (Thanks to Stefan Novak)
Color palettes generated by
brewer_pal no longer give warnings when fewer
than 3 colors are requested. (Winston Chang)
functions have been added, for scaling the area of points to be proportional to their value. These are used byscale_size_area` in ggplot2.
zero_range has improved behaviour thanks to Brian Diggs.
brewer_pal complains if you give it an incorrect palette type. (Fixes #15,
thanks to Jean-Olivier Irisson)
shape_pal warns if asked for more than 6 values. (Fixes #16, thanks to
time_trans gains an optional argument
tz to specify the time zone to use
for the times. If not specified, it will be guess from the first input with
a non-null time zone.
time_trans now check that their inputs are of the correct
type. This prevents ggplot2 scales from silently giving incorrect outputs
when given incorrect inputs.
Change the default breaks algorithm for
Previously it was
pretty_breaks(), and now it's
which uses the
extended() algorithm from the labeling package.
fixed namespace problem with
train_continuous so zero-row or all infinite data
frames don't potentially cause problems.
check for zero-length colour in
extended_breaks which implements an extension to Wilkinson's
labelling approach, as implemented in the
labeling package. This should
generally produce nicer breaks than
alpha can now preserve existing alpha values if
alpha is missing.
log_breaks always gives breaks evenly spaced on the log scale, never
evenly spaced on the data scale. This will result in really bad breaks for
some ranges (e.g 0.5-0.6), but you probably shouldn't be using log scales in
that situation anyway.
only.finite argument and default to operating
only on finite values. This is needed for ggplot2, and reflects the use of
Inf and -Inf as special values.
bounds functions now
force evaluation of range to avoid bug with S3
method dispatch inside primitive functions (e.g.
Simplified algorithm for
discrete_range that is robust to
stringsAsFactors global option. Now, the order of a factor will only be
preserved if the full factor is the first object seen, and all subsequent
inputs are subsets of the levels of the original factor.
scientific ensures output is always in scientific format and off the
specified number of significant digits.
comma ensures output is never in
scientific format. (Fixes #7)
Another tweak to
zero_range to better detect when a range has zero length.