# Cookbook

This cookbook provides examples of the code used to produce various chart types using sgplot. There are also examples to demonstrate how to apply further customisation to sgplot charts.

If there is a chart type or task which you think would be useful to include here, please submit a suggestion.

use_sgplot
The examples in this cookbook use the sgplot theme and colour functions explicitly, however it may be easier to make use of the `use_sgplot()` function if your charts all require a similar style. More information on `use_sgplot` can be found on the homepage.

Note on use of titles, subtitles and captions
Titles, subtitles and captions have been embedded in the charts in this cookbook for demonstration purposes. However, for accessibility reasons, it is usually preferable to provide titles in the body of the page rather than embedded within the image of the plot.

The following packages are required to produce the example charts in this cookbook:

    library(sgplot)
    library(ggplot2)
    library(dplyr)

    # Use gapminder data for cookbook charts
    library(gapminder)

## Line charts

### Line chart with one line

    gapminder |>
      filter(country == "United Kingdom") |>
      ggplot(aes(x = year, y = lifeExp)) +
      geom_line(linewidth = 1, colour = sg_colour_values["dark-blue"]) +
      theme_sg() +
      scale_y_continuous(limits = c(0, 82),
                         breaks = seq(0, 80, 20),
                         expand = c(0, 0)) +
      scale_x_continuous(breaks = seq(1952, 2007, 5)) +
      labs(
        x = "Year",
        y = NULL,
        title = "Living Longer",
        subtitle = "Life Expectancy in the United Kingdom 1952-2007",
        caption = "Source: Gapminder"
      )

### Line chart with multiple lines

    gapminder |>
      filter(country %in% c("United Kingdom", "China")) |>
      ggplot(aes(x = year, y = lifeExp, colour = country)) +
      geom_line(linewidth = 1) +
      theme_sg(legend = "bottom") +
      scale_colour_discrete_sg() +
      scale_y_continuous(limits = c(0, 82),
                         breaks = seq(0, 80, 20),
                         expand = c(0, 0)) +
      scale_x_continuous(breaks = seq(1952, 2007, 5)) +
      labs(
        x = "Year",
        y = NULL,
        title = "Living Longer",
        subtitle = "Life Expectancy in the United Kingdom and China 1952-2007",
        caption = "Source: Gapminder",
        colour = NULL
      )

An example with line labels and no legend can be found in the Adding annotations section.

## Bar charts

    bar_data <-
      gapminder |>
      filter(year == 2007 & continent == "Europe") |>
      slice_max(order_by = lifeExp, n = 5)

    ggplot(bar_data, aes(x = reorder(country, -lifeExp), y = lifeExp)) +
      geom_col(fill = sg_colour_values["dark-blue"]) +
      theme_sg() +
      scale_y_continuous(expand = c(0, 0)) +
      labs(
        x = NULL,
        y = NULL,
        title = "Iceland has the highest life expectancy in Europe",
        subtitle = "Life expectancy in European countries, 2007",
        caption = "Source: Gapminder"
      )

A bar chart can sometimes look better with horizontal bars. This can also be a good option if your bar labels are long and difficult to display horizontally on the x axis. To produce a horizontal bar chart, swap the variables defined for x and y in `aes()` and make a few tweaks to `theme_sg()`; draw grid lines for the x axis only by setting the `grid` argument, and draw an axis line for the y axis only by setting the `axis` argument.

    ggplot(bar_data, aes(x = lifeExp, y = reorder(country, lifeExp))) +
      geom_col(fill = sg_colour_values["dark-blue"]) +
      theme_sg(grid = "x", axis = "y") +
      scale_x_continuous(expand = c(0, 0)) +
      labs(
        x = NULL,
        y = NULL,
        title = "Iceland has the highest life expectancy in Europe",
        subtitle = "Life expectancy in European countries, 2007",
        caption = "Source: Gapminder"
      )

### Grouped bar chart

To create a grouped bar chart, set `stat = "identity"` and `position = "dodge"` in the call to `geom_bar()`. Also assign a variable to `fill` within `aes()` to determine what variable is used to create bars within groups. The `legend` argument in `theme_sg()` can be used to set the position of the legend.

    grouped_bar_data <-
      gapminder |>
      filter(year %in% c(1967, 2007) &
               country %in% c("United Kingdom", "Ireland", "France", "Belgium"))

    ggplot(grouped_bar_data,
           aes(x = country, y = lifeExp, fill = as.factor(year))) +
      geom_bar(stat = "identity", position = "dodge") +
      scale_y_continuous(expand = c(0, 0)) +
      theme_sg(legend = "bottom") +
      scale_fill_discrete_sg() +
      labs(
        x = "Country",
        y = NULL,
        fill = NULL,
        title = "Living longer",
        subtitle = "Difference in life expectancy, 1967-2007",
        caption = "Source: Gapminder"
      )

### Stacked bar chart

To create a stacked bar chart, set `stat = "identity` and `position = "fill"` in the call to `geom_bar()` and assign a variable to `fill` as before. This will plot your data as part-to-whole. To plot counts, set `position = "identity"`.

Caution should be taken when producing stacked bar charts. They can quickly become difficult to interpret if plotting non part-to-whole data, and/or if plotting more than two categories per stack. First and last categories in the stack will always be easier to compare across bars than those in the middle. Think carefully about the story you are trying to tell with your chart.

    stacked_bar_data <-
      gapminder |>
      filter(year == 2007) |>
      mutate(lifeExpGrouped = cut(lifeExp,
                                  breaks = c(0, 75, Inf),
                                  labels = c("Under 75", "75+"))) |>
      group_by(continent, lifeExpGrouped) |>
      summarise(n_countries = n(), .groups = "drop")

    ggplot(stacked_bar_data,
           aes(x = continent, y = n_countries, fill = lifeExpGrouped)) +
      geom_bar(stat = "identity", position = "fill") +
      theme_sg(legend = "bottom") +
      scale_y_continuous(expand = c(0, 0), labels = scales::percent) +
      coord_cartesian(clip = "off") +
      scale_fill_discrete_sg() +
      labs(
        x = NULL,
        y = NULL,
        fill = "Life Expectancy",
        title = "How life expectancy varies across continents",
        subtitle = "Percentage of countries by life expectancy band, 2007",
        caption = "Source: Gapminder"
      )

## Histograms

    gapminder |>
      filter(year == 2007) |>
      ggplot(aes(x = lifeExp)) +
      geom_histogram(binwidth = 5,
                     colour = "white",
                     fill = sg_colour_values["dark-blue"]) +
      theme_sg() +
      scale_y_continuous(expand = c(0, 0)) +
      labs(
        x = NULL,
        y = "Number of \ncountries",
        title = "How life expectancy varies",
        subtitle = "Distribution of life expectancy, 2007",
        caption = "Source: Gapminder"
      )

## Scatterplots

    gapminder |>
      filter(year == 2007) |>
      ggplot(aes(x = gdpPercap, y = lifeExp, size = pop)) +
      geom_point(colour = sg_colour_values["dark-blue"]) +
      theme_sg(axis = "none", grid = "xy") +
      scale_x_continuous(
        labels = function(x) scales::dollar(x, prefix = "£")
      ) +
      scale_size_continuous(labels = scales::comma) +
      labs(
        x = "GDP",
        y = "Life\nExpectancy",
        size = "Population",
        title = stringr::str_wrap(
          "The relationship between GDP and Life Expectancy is complex", 40
        ),
        subtitle = "GDP and Life Expectancy for all countires, 2007",
        caption = "Source: Gapminder"
      )

## Small multiples

    gapminder |>
      filter(continent != "Oceania") |>
      group_by(continent, year) |>
      summarise(pop = sum(as.numeric(pop)), .groups = "drop") |>
      ggplot(aes(x = year, y = pop, fill = continent)) +
      geom_area() +
      theme_sg(axis = "none", ticks = "none", legend = "none") +
      scale_fill_discrete_sg() +
      facet_wrap(~ continent, ncol = 2) +
      scale_y_continuous(breaks = c(0, 2e9, 4e9),
                         labels = c(0, "2bn", "4bn")) +
      coord_cartesian(clip = "off") +
      theme(axis.text.x = element_blank()) +
      labs(
        x = NULL,
        y = NULL,
        title = "Asia's rapid growth",
        subtitle = "Population growth by continent, 1952-2007",
        caption = "Source: Gapminder"
      )

## Pie charts

    stacked_bar_data |>
      filter(continent == "Europe") |>
      ggplot(aes(x = "", y = n_countries, fill = lifeExpGrouped)) +
      geom_col(colour = "white", position = "fill") +
      coord_polar(theta = "y") +
      theme_sg(grid = "none", axis = "none", ticks = "none") +
      theme(axis.text = element_blank()) +
      scale_fill_discrete_sg() +
      labs(
        x = NULL,
        y = NULL,
        fill = NULL,
        title = "How life expectancy varies in Europe",
        subtitle = "Percentage of countries by life expectancy band, 2007",
        caption = "Source: Gapminder"
      )

## Focus charts

    bar_data |>
      ggplot(
        aes(x = reorder(country, -lifeExp), y = lifeExp,
            fill = country == "Sweden")
      ) +
      geom_col() +
      theme_sg(legend = "none") +
      scale_y_continuous(expand = c(0, 0)) +
      scale_fill_discrete_sg("focus", reverse = TRUE) +
      labs(
        x = NULL,
        y = NULL,
        title = "Sweden has the fourth highest life expectancy in Europe",
        subtitle = "Life expectancy in European countries, 2007",
        caption = "Source: Gapminder"
      )

## Interactive charts

To make a `ggplot2` chart interactive, use `ggplotly()` from the `plotly` package. Note however that `ggplotly()` has a number of ‘quirks’, including the following:

- sgplot uses the ‘sans’ font family, however `plotly` does not recognise this font. To work around this you should add a further call to `theme` to set the font family for text to `""`.

- Subtitles and captions are not supported in `ggplotly()`. As stated elsewhere in this guidance, titles and subtitles should ideally be included in the body of text surrounding a chart rather than embedded in the chart itself, and so this is hopefully not a big issue. This example therefore has no title, subtitle or caption.

    p <-
      bar_data |>
      # Format text for tooltips
      mutate(tooltip = paste0(
        "Country: ", country, "\n",
        "Life Expectancy: ", round(lifeExp, 1)
      )) |>
      ggplot(aes(x = reorder(country, -lifeExp), y = lifeExp, text = tooltip)) +
      geom_col(fill = sg_colour_values["dark-blue"]) +
      theme_sg(ticks = "x") +
      theme(text = element_text(family = "")) +
      scale_y_continuous(expand = c(0, 0)) +
      labs(
        x = NULL,
        y = NULL
      )

    plotly::ggplotly(p, tooltip = "text") |>
      plotly::config(
        modeBarButtons = list(list("resetViews")),
        displaylogo = FALSE
      )

sgplot currently only works with `ggplot2` charts, however there are plans to develop the package further to support interactive Highcharts produced using the `highcharter` package.

## Annotations

Labelling your chart is often preferable to using a legend, as often this relies on a user matching the legend to the data using colour alone. The legend can be removed from a chart by setting `legend = "none"` in `theme_sg()`.

The easiest way to add an annotation is to manually define the co-ordinates of the required position.

    ann_data <- gapminder |>
      filter(country %in% c("United Kingdom", "China"))

    ann_data |>
      ggplot(aes(x = year, y = lifeExp, colour = country)) +
      geom_line(linewidth = 1) +
      theme_sg(legend = "none") +
      scale_colour_discrete_sg() +
      scale_y_continuous(limits = c(0, 82),
                         breaks = seq(0, 80, 20),
                         expand = c(0, 0)) +
      scale_x_continuous(limits = c(1952, 2017),
                         breaks = seq(1952, 2017, 5)) +
      annotate(geom = "label", x = 2008, y = 73, label = "China",
               colour = sg_colour_values[1],
               label.size = NA,
               hjust = 0, vjust = 0.5) +
      annotate(geom = "label", x = 2008, y = 79.4, label = "United Kingdom",
               colour = sg_colour_values[2],
               label.size = NA,
               hjust = 0, vjust = 0.5) +
      labs(
        x = "Year",
        y = NULL,
        title = "Living Longer",
        subtitle = "Life Expectancy in the United Kingdom and China 1952-2007",
        caption = "Source: Gapminder"
      )

However, this makes the code difficult to reuse as values are hard coded and not automatically generated from the data. Automating the position of annotations is possible, but more fiddly.

The following examples use `geom_label()` to use values from the data to position annotations. `geom_label()` draws a rectangle behind the text (white by default) and a border the same colour as the text (`label_size = NA` can be used to remove the border). `geom_text()` is also an option for annotations, but this does not include a background and so can be harder for text to read if it overlaps with other chart elements. These functions also have `nudge` arguments that can be used to displace text to improve the positioning.

Note that in the previous examples, `annotate()` also requires a geom (`label` or `text`). These operate in the same way as `geom_label()` and `geom_text()`, but as discussed, `annotate()` is only able to deal with fixed values.

    ann_labs <- ann_data |>
      group_by(country) |>
      mutate(min_year = min(year)) |>
      filter(year == max(year)) |>
      ungroup()

    ann_data |>
      ggplot(aes(x = year, y = lifeExp, colour = country)) +
      geom_line(linewidth = 1) +
      theme_sg(legend = "none") +
      scale_colour_discrete_sg() +
      scale_y_continuous(limits = c(0, 82),
                         breaks = seq(0, 80, 20),
                         expand = c(0, 0)) +
      scale_x_continuous(limits = c(1952, 2017),
                         breaks = seq(1952, 2017, 5)) +
      geom_label(data = ann_labs,
                 aes(x = year, y = lifeExp, label = country, colour = country),
                 hjust = 0,
                 vjust = 0.5,
                 nudge_x = 0.5,
                 label.size = NA) +
      labs(
        x = "Year",
        y = NULL,
        title = "Living Longer",
        subtitle = "Life Expectancy in the United Kingdom and China 1952-2007",
        caption = "Source: Gapminder"
      )

Annotations may also be used to add value labels to a bar chart. Note that `geom_text()` is used here as a background is not required.

    ggplot(bar_data, aes(x = reorder(country, -lifeExp), y = lifeExp)) +
      geom_col(fill = sg_colour_values["dark-blue"]) +
      geom_text(aes(label = round(lifeExp, 1)),
                nudge_y = -5, colour = "white") +
      theme_sg() +
      scale_y_continuous(expand = c(0, 0)) +
      labs(
        x = NULL,
        y = NULL,
        title = "Iceland has the highest life expectancy in Europe",
        subtitle = "Life expectancy in European countries, 2007",
        caption = "Source: Gapminder"
      )

Note: The `annotate()` function should be used to add annotations with manually defined positioning co-ordinates, whereas `geom_label()` and `geom_text()` should be used when using co-ordinates defined in a data frame. Although the reverse may work, text can appear blurry.

## Other customisations

`theme_sg()` has arguments to control the legend position and appearance of grid lines, axis lines and axis ticks. More information on accepted values can be found in the help file.

### Sorting a bar chart

To control the order of bars in a chart, wrap the variable you want to arrange with `reorder()` and specify what variable you want to sort by. The following example sorts bars in ascending order of life expectancy. To sort in descending order, you would change this to `reorder(country, desc(lifeExp))`.

    bar_data |>
      ggplot(aes(x = lifeExp, y = reorder(country, lifeExp))) +
      geom_col(fill = sg_colour_values["dark-blue"]) +
      theme_sg(axis = "y", grid = "x")

Examples in the following sections build on this chart.

### Changing chart titles

Chart titles such as the main title, subtitle, caption, axis titles and legend titles, can be controlled using `labs()`. A title can be removed using `NULL`.

    last_plot() +
      labs(
        x = NULL,
        y = NULL,
        title = "Iceland has the highest life expectancy in Europe",
        subtitle = "Life expectancy in European countries, 2007",
        caption = "Source: Gapminder"
      )

### Reducing space between chart and axis

By default, a bar chart will have a gap between the bottom of the bars and the axis. This can be removed as follows:

    last_plot() + scale_x_continuous(expand = c(0, 0))

The equivalent adjustment can be made for the y axis using `scale_y_continuous`.

### Changing axis limits, breaks and labels

Axis limits, breaks and labels for continuous variables can be controlled using `scale_x/y_continuous()`. For discrete variables, labels can be changes using `scale_x/y_discrete()` or alternatively by recoding the variable in the data before creating a chart.

    last_plot() +
      scale_x_continuous(expand = c(0, 0),
                         limits = c(0, 85),
                         breaks = seq(0, 80, 20),
                         labels = c(seq(0, 70, 20), "80 years"))

Note that further calls to `scale_x/y_continuous` will overwrite previous calls, hence why `expand = c(0, 0)` has been included again in this example.

### Formatting labels

Formatting axis labels or legend labels is easily handled using the `scales` package. The following example formats y axis labels as percentages, however `scales` can also handle currency and thousands separators.

    stacked_bar_data |>
      ggplot(aes(x = continent, y = n_countries, fill = lifeExpGrouped)) +
      geom_bar(stat = "identity", position = "fill") +
      theme_sg(legend = "bottom") +
      scale_y_continuous(expand = c(0, 0), labels = scales::percent) +
      scale_fill_discrete_sg() +
      labs(
        x = NULL,
        y = NULL,
        fill = "Life Expectancy",
        title = "How life expectancy varies across continents",
        subtitle = "Percentage of countries by life expectancy band, 2007",
        caption = "Source: Gapminder"
      )

### Avoiding axis/grid lines being cut off

Axis lines and grid lines can sometimes appear ‘cut off’ if they are drawn at the limits of the chart range. You can see in the example in the previous section that the top grid line is slightly narrower than the adjacent tick mark on the y axis. This is because the y axis limit is 100%. As the grid line is centred at 100%, the top half of the line is ‘cut off’. This can be corrected as follows:

    last_plot() + coord_cartesian(clip = "off")

### Adding a line

To add a horizontal or vertical line across the whole plot, use `geom_hline()` or `geom_vline()`. This can be useful to highlight a threshold or average level.

    gapminder |>
      filter(country == "United Kingdom") |>
      ggplot(aes(x = year, y = lifeExp)) +
      geom_line(linewidth = 1, colour = sg_colour_values[1]) +
      geom_hline(yintercept = 75, colour = sg_colour_values[2],
                 linewidth = 1, linetype = "dashed") +
      annotate(geom = "text", x = 2007, y = 70, label = "Age 70") +
      theme_sg() +
      scale_y_continuous(limits = c(0, 82),
                         breaks = seq(0, 80, 20),
                         expand = c(0, 0)) +
      scale_x_continuous(breaks = seq(1952, 2007, 5)) +
      labs(
        x = "Year",
        y = NULL,
        title = "Living Longer",
        subtitle = "Life Expectancy in the United Kingdom 1952-2007",
        caption = "Source: Gapminder"
      )

### Wrapping text

If text is too long, it may be cut off or distort the dimensions of the chart.

    plot <-
      ggplot(bar_data, aes(x = reorder(country, -lifeExp), y = lifeExp)) +
      geom_col(fill = sg_colour_values["dark-blue"]) +
      theme_sg() +
      scale_y_continuous(expand = c(0, 0)) +
      labs(
        x = NULL,
        subtitle = "Life expectancy in European countries, 2007",
        caption = "Source: Gapminder"
      )

    plot +
      labs(
        y = "Percentage of countries",
        title = paste("Iceland has the highest life expectancy in Europe",
                      "followed closely by Switzerland")
      )

There are two suggested ways to solve this issue; Insert `\n` within a string to force a line break; Use `stringr::str_wrap()` to set a maximum character width of the string. See examples of both of these methods as follows:

    plot +
      labs(
        y = "Percentage\nof countries",
        title = stringr::str_wrap(
          paste("Iceland has the highest life expectancy in Europe",
                "followed closely by Switzerland"),
          width = 50
        )
      )

### Adjusting theme elements

If you find you need to adjust theme elements for your chart, this can be done using `theme()`. Note that this should be done after the call to `theme_sg()`, otherwise `theme_sg()` may overwrite the specifications you’ve made.

    ggplot(bar_data, aes(x = reorder(country, -lifeExp), y = lifeExp)) +
      geom_col(fill = sg_colour_values["dark-blue"]) +
      theme_sg(axis = "xy") +
      theme(axis.line = element_line(colour = "black"),
            axis.ticks = element_line(colour = "black")) +
      scale_y_continuous(expand = c(0, 0)) +
      labs(
        x = NULL,
        y = NULL,
        title = "Iceland has the highest life expectancy in Europe",
        subtitle = "Life expectancy in European countries, 2007",
        caption = "Source: Gapminder"
      )

## Using different colour palettes

sgplot provides colour palettes as set out by the Scottish Government Design System. These palettes have been developed to meet the Web Content Accessibility Guidelines 2.1 for graphical objects.

The main palette is the default for discrete colour/fill functions, and the sequential palette for continuous colour/fill functions.

The Scottish Government palettes are used by default, however palettes are also available for Social Security Scotland and the Government Analysis Function.

More information on the colours used in sgplot can be found at `vignette("colours")`.

### Using non-default sgplot colour palettes

There may be instances where you want to use an sgplot colour palette other than the default. The full list of available palettes can be found by running either `sgplot::sg_colour_palettes` or `sgplot::af_colour_palettes`.

To use the Scottish Government `main-extended` palette:

    gapminder |>
      filter(country %in% c("United Kingdom", "China", "India",
                            "Sweden", "Namibia", "Brazil")) |>
      ggplot(aes(x = year, y = lifeExp, colour = country)) +
      geom_line(linewidth = 1) +
      theme_sg(legend = "bottom") +
      scale_colour_discrete_sg("main-extended") +
      scale_y_continuous(limits = c(0, 82),
                         breaks = seq(0, 80, 20),
                         expand = c(0, 0)) +
      scale_x_continuous(breaks = seq(1952, 2007, 5)) +
      labs(
        x = "Year",
        y = NULL,
        title = "Living Longer",
        subtitle = "Life Expectancy in the United Kingdom and China 1952-2007",
        caption = "Source: Gapminder",
        colour = NULL
      )

Note: This chart is for demonstration purposes only. Accessibility guidance recommends using a maximum of four colours to avoid clutter.

To use an Analysis Function palette, set `palette_type = "af"` when using any of the `scale_` colour functions. For example, to use the Analysis Function `main2` palette:

    gapminder |>
      filter(country %in% c("United Kingdom", "China")) |>
      ggplot(aes(x = year, y = lifeExp, colour = country)) +
      geom_line(linewidth = 1) +
      theme_sg(legend = "bottom") +
      scale_colour_discrete_sg("main2", palette_type = "af") +
      scale_y_continuous(limits = c(0, 82),
                         breaks = seq(0, 80, 20),
                         expand = c(0, 0)) +
      scale_x_continuous(breaks = seq(1952, 2007, 5)) +
      labs(
        x = "Year",
        y = NULL,
        title = "Living Longer",
        subtitle = "Life Expectancy in the United Kingdom and China 1952-2007",
        caption = "Source: Gapminder",
        colour = NULL
      )

### Using your own colour palette

There may be instances where you’d like to use a colour palette that is not available in sgplot. If so, this should be carefully considered to ensure it meets accessibility requirements. The Analysis Function guidance outlines appropriate steps for choosing your own accessible colour palette and should be used.

    my_palette <- c("#0F820D", "#000000")

    gapminder |>
      filter(country == "United Kingdom") |>
      ggplot(aes(x = year, y = lifeExp)) +
      geom_line(linewidth = 1, colour = my_palette[1]) +
      theme_sg() +
      scale_y_continuous(limits = c(0, 82),
                         breaks = seq(0, 80, 20),
                         expand = c(0, 0)) +
      scale_x_continuous(breaks = seq(1952, 2007, 5)) +
      labs(
        x = "Year",
        y = NULL,
        title = "Living Longer",
        subtitle = "Life Expectancy in the United Kingdom 1952-2007",
        caption = "Source: Gapminder"
      )

    gapminder |>
      filter(country %in% c("United Kingdom", "China")) |>
      ggplot(aes(x = year, y = lifeExp, colour = country)) +
      geom_line(linewidth = 1) +
      theme_sg(legend = "bottom") +
      scale_colour_manual(values = my_palette) +
      scale_y_continuous(limits = c(0, 82),
                         breaks = seq(0, 80, 20),
                         expand = c(0, 0)) +
      scale_x_continuous(breaks = seq(1952, 2007, 5)) +
      labs(
        x = "Year",
        y = NULL,
        title = "Living Longer",
        subtitle = "Life Expectancy in the United Kingdom and China 1952-2007",
        caption = "Source: Gapminder",
        colour = NULL
      )

#### Adding a new colour palette to sgplot

If you use a different palette regularly and feel it would be useful for this to be added to sgplot, please make a suggestion as per the contributing guidance.

## Acknowledgments

This cookbook and the examples it contains have been inspired by the BBC Visual and Data Journalism cookbook for R graphics and their bbplot package.