create_palette: Create a color palette
In jfjelstul/eumaps: Tools to make maps of the European Union

Description Usage Arguments Details Value Examples

View source: R/create_palette.R

This function creates a color palette for a map of the European Union (EU) made by eumaps::make_map(). It creates a object of type eumaps.palette, which you can pass to the palette argument of make_map(). An eumaps.palette object creates a mapping between a continuous variable and a color ramp with a fixed number of colors. It also defines the colors and labels to use for member states with missing data, member states where the data is not applicable, and non-member states.

An eumaps.palette object only defines the colors used for shading countries on the map. It does not define the background color (i.e., the color of the water), the color of country borders, or the color of the border around the map, These are defined using create_theme(), which returns an eumaps.theme object that you can pass to the theme argument of make_map().

create_palette(
  member_states,
  values,
  not_applicable = NULL,
  value_min,
  value_max,
  count_colors,
  color_low,
  color_high,
  color_mid = NULL,
  color_missing = c(0.75, 0.75, 0.75),
  color_not_applicable = c(0.85, 0.85, 0.85),
  color_non_member_state = c(0.95, 0.95, 0.95),
  label_missing = "Missing",
  label_not_applicable = "Not applicable",
  label_non_member_state = "Not a member state"
)

`member_states`	String. Required, without a default value. A vector that contains member state names. Needs to be the same length as `values`. You can run `list_member_states()` to get a list of valid member state names. Member state names should not be repeated.
`values`	Numeric. Required, without a default value. A vector that contains values corresponding to each member state in `member_states` to be used for shading the member states. Needs to be the same length as `member_states`.
`not_applicable`	String. Optional. A vector of member states to code as not applicable. These member states will not be shaded using the color ramp. You can run `list_member_states()` to get a list of valid member state names. The default value is `NULL`.
`value_min`	Numeric. Required, without a default value. The value of the data that corresponds to the lower bound of the bin for the lowest color in the gradient. Should be a reasonably rounded value that is just less than the minimum value that occurs in the data.
`value_max`	Numeric. Required, without a default value. The value of the data that corresponds to the upper bound of the bin for the highest color in the gradient. Should be a reasonably rounded value that is just greater than the maximum value that occurs in the data.
`count_colors`	Numeric. Required, without a default value. The number of colors to use in the discrete gradient. The minimum is 2 and the maximum is 10.
`color_low`	Color.. Required (does not have a default). The color to use for the low end of the gradient. Can be any value accepted by `convert_color()`.
`color_high`	Color. Required, without a default value. The color to use for the high end of the gradient. Can be any value accepted by `convert_color()`.
`color_mid`	Color. Optional. The color to use for the middle of the gradient. Specifying a value creates a diverging color palette. Usually you want this color to be white. Can be any value accepted by `convert_color()`. The default value is `NULL`.
`color_missing`	Color. Required, with a default value. The color to use for member states with missing data. Can be any value accepted by `convert_color()`. The default value is `c(0.75, 0.75, 0.75)`.
`color_not_applicable`	Color. Required, with a default value. The color to use for member states that are coded as not applicable. Can be any value accepted by `convert_color()`. The default value is `c(0.85, 0.85, 0.85)`.
`color_non_member_state`	Color. Required, with a default value. The color to use for non-member states. Can be any value accepted by `convert_color()`. The default value is `c(0.95, 0.95, 0.95)`.
`label_missing`	String. Required, with a default value. The label to use in the legend for the color for member states with missing data. The default value is `Missing`.
`label_not_applicable`	String. Required, with a default value. The label to use in the legend for the color for member states that are coded as not applicable. The default value is `Not applicable`.
`label_non_member_state`	String. Required, with a default value. The label to use in the legend for the color for non-member states. The default value is `Not a member state`.

This function creates a mapping between a continuous variable and a color ramp with a fixed number of colors. To make a palette, you need to provide two vectors: a vector that contains member state names and a vector that contains values corresponding to each member state to be used for shading the member states. Member state names should not be repeated. You can run list_member_states() to get a list of valid member state names. The function will map the values you provide to colors.

You also need to specify minimum and maximum data values (these values should be reasonably rounded, and all of the data points that you want to plot should fall within this range), a low color and a high color for the color ramp (there is also an optional middle color, so you can create a diverging color palette), and the number of colors in the color ramp (usually, for a choropleth map, you do not want to plot more than 10 colors).

The number of colors in the color ramp determines the number of bins that the data will be divided into. The number of bins is always the same as the number of colors. The break points between the bins (the number of break points is always 1 less than the number of colors/bins) will be evenly spaced between the minimum and maximum data values you provide.

You can also use create_palette() to specify the colors to use for member states with missing data, for member states where the data is not applicable, and for non-member states, along with the labels to use for these three categories in the map legend. These three colors only appear in the legend when applicable. In other words, the color for missing values doesn't appear in the legend if there are no missing values, the color for member states where the data is not applicable states doesn't appear if the data is applicable to all member states, and the color for non-member states doesn't appear if non-member states are not plotted.

This function returns an object of type eumaps.palette, which you can pass to the palette argument of make_maps().

# using the default values
data <- simulate_data()
palette <- create_palette(
  member_states = data$member_state,
  values = data$variable,
  value_min = 0,
  value_max = 1,
  count_colors = 8,
  color_low = "#3498DB",
  color_high = "#E74C3C",
  color_mid = "#FFFFFF"
)

# using all options
data <- simulate_data()
palette <- create_palette(
  member_states = data$member_state,
  values = data$variable,
  not_applicable = NULL,
  value_min = 0,
  value_max = 1,
  count_colors = 8,
  color_low = "#3498DB",
  color_high = "#E74C3C",
  color_mid = "#FFFFFF",
  color_missing = c(0.75, 0.75, 0.75),
  color_not_applicable = c(0.85, 0.85, 0.85),
  color_non_member_state = c(0.95, 0.95, 0.95),
  label_missing = "Missing",
  label_not_applicable = "Not applicable",
  label_non_member_state = "Not a member state"
)