dftplotr
dftplotR
dftplotR is an R package to provide standardised charts formatting in ggplot2. It includes theme functions which meet Government Statistical Service (GSS) best practice guidance. It also includes colour palettes based on DfT corporate branding which meet WCAG 2.0 accessibility standards, and are distinguishable in greyscale.
Installation
The package can be installed directly from Github using the remotes
install_github call
install.packages("remotes")
remotes::install_github("department-for-transport-public/dftplotr")
Overview
The package contains the following functions:
scale_colour_dft: ggplot function which applies one of a range of DfT
palettes to a ggplot line chart (or other chart which groups by
colour)
scale_fill_dft: ggplot function which applies one of a range of DfT
palettes to a ggplot line chart (or other chart which groups by
fill)
display_palette: a visual output which shows all of the colours
contained in the selected DfT palette
theme_general_dft; ggplot function which applies a standardised theme
to all ggplot charts.
theme_bar_dft; ggplot function which applies a standardised theme to
ggplot bar chart. There are options to pick other dft color palettes and
top flip the x and y axis. This theme also sets the x-axis intercept at
y to 0.
theme_line_dft; ggplot function which applies a standardised theme to
a ggplot line chart. There are options to pick other dft color palettes.
This theme also sets the x-axis intercept at y to 0.
Colour palettes
The dftplotR package comes with 9 pre-loaded palettes. These contain colours taken from the DfT corporate colour scheme, and have also been selected to meet accessibility guidance.
The palettes and the colours in them can be seen here, or visualised
within the package by calling display.palette() and the palette name.
Accessible colours
These new colours were designed to be more accessible. Each colour has a high contrast with both white and with the adjacent colours. In order to make your charts more accessible, it is recommended to use the palettes presented below.
Legacy colours
The dftplotr package also includes other legacy palettes, which are not as
accessible as the ones recommended above. The two primary palettes are
main.palette; a desaturated palette ideal for use in bar charts or
other area fill charts, and electric.brights, a saturated palette
which improves visibility in line-charts or other point colour charts.
The other palettes are ideal where these palettes are not appropriate,
or where variation is needed.
Gradient palettes
The dftplotR package also comes with 6 gradient palettes. These have defined start and end colours taken from the DfT corporate colour scheme, and will auto-generate shades between these two points to create the specified number of colours. These do not meet accessibility guidance, and should only be used when the pre-set palettes are not appropriate and colour is not conveying the primary message of the visualisation.
The palettes and the colours in them can be seen here, or visualised
within the package by calling display.palette(gradient = TRUE) and the
palette name. The number of shades in the palette can be specified using
the n = argument, e.g. n = 8 for a palette with 8 shades. When this
argument is not used, the default number of shades is 5. Example
gradient palettes with 5 shades can be seen below:
ggplot2 themes
The dftplotR package comes with three standard themes to apply to charts.
The theme_general_dft theme can be applied to any ggplot chart type
and is used as a base for the other two more specific themes.
The theme_bar_dft theme work best with bar charts. It gives the
flexibility of customising the final plot with options for changing the
colour palette, moving the legend position and flipping the x and y-axis
around when x-axis labels are too long. It also sets the intercept of
the x-axis with the y-axis to 0.
The theme_line_dft theme works best with line charts. It gives he
flexibility of customising the final plot with options for changing the
colour paletter. It also labels lines with the label name and sets the
intercept of the x-axis with the y-axis to 0.
The difference between a bar plot without themeing and one with the
theme_bar_dft theme can be seen below:
Palette picker tool
The palette picker tool is a Shiny tool which is now available directly here instead of bundled into the package. This tool allows visualisation of all DfT corporate colours in two chart formats; line and bar, to allow you to build and visualise your own custom palettes.
It contains options to allow you to select a WCAG 2.0 accessibility rating you require the palette to meet, and functions to show what that palette looks like in grayscale and with the most common forms of colour-blindness.
This tool is ideal to facilitate building your own palettes for use in applications outside of statistical publications, while still conforming to the DfT corporate colours and GSS accessibility guidance.
Accessibility
The dftplotr colour palettes aim to be accessible to those with the most common forms of colour blindness, and should also be discernable in greyscale. The standard palettes in this package have been designed to meet WCAG 2.0 accessibility guidance.
Two of the created accessible palettes (travel.direction, country.lane)
contain 8 colours each, and only one accessible palette (joyful.journey)
contains 6 colours each, and meet WCAG 2.0 AAA guidance.
Four of the created legacy palettes (main.palette, electric.brights,
just.beachy and cycling.hills) have a contrast ratio of at least
4.5:1 to the bars adjacent to them, and alternate light and dark shades
to further increase contrast. This is the highest standard of
accessibility and should be used when possible.
Two of the created legacy palettes (mountain.train and clear.skies) have a
contrast ration of at least 3:1 to the bars adjacent to them, and
alternate light and dark shades to further increase contrast. This is
the minimum standard of accessibility required for publication and use
should be limited to times when a larger palette is required.
It is also possible to generate gradient palettes using this package, with colours based on the DfT corporate theme. While these palettes can be generated with any number of shades, there is no guarantee that the contrast between these colours is sufficient to meet accessibility standards. These palettes should only be used in very limited circumstances where colour is not the only means of distinguishing different groupings and none of the standard palettes are suitable.
For line charts, it may be possible that lines with reduced contrast are next to each other. As a result, and in line with GSS recommendation, line charts should be labelled directly where possible rather than using a legend.