mapgl (version 0.3)

interpolate_palette: Create an interpolation expression with automatic palette and break calculation

Description

This function creates an interpolation expression by automatically calculating break points using different methods and applying a color palette. It handles the values/stops matching automatically and supports the same classification methods as the step functions.

Usage

interpolate_palette(
  data = NULL,
  column,
  data_values = NULL,
  method = "equal",
  n = 5,
  palette = NULL,
  colors = NULL,
  na_color = "grey"
)

Value

A list of class "mapgl_continuous_scale" containing the interpolation expression and metadata.

Arguments

data

A data frame or sf object containing the data. If provided, data_values will be extracted from data[[column]]. Either data or data_values must be provided.

column

The name of the column to use for the interpolation.

data_values

A numeric vector of the actual data values used to calculate breaks. If NULL and data is provided, will be extracted from data[[column]].

method

The method for calculating breaks. Options are "equal" (equal intervals), "quantile" (quantile breaks), or "jenks" (Jenks natural breaks). Defaults to "equal".

n

The number of break points to create. Defaults to 5.

palette

A function that takes n and returns a character vector of colors. If NULL and colors is also NULL, defaults to viridisLite::viridis.

colors

A character vector of colors to use. If provided, these colors will be interpolated to match the number of breaks if needed. Either palette or colors should be provided, but not both.

na_color

The color to use for missing values. Defaults to "grey".

Examples

if (FALSE) {
# Create continuous color scale - using palette function
my_data <- data.frame(value = c(10, 25, 30, 45, 60, 75, 90))
scale1 <- interpolate_palette(data = my_data, column = "value",
                             method = "equal", n = 5, palette = viridisLite::plasma)

# Using specific colors (will interpolate to 5 if needed)
scale2 <- interpolate_palette(data = my_data, column = "value",
                             method = "equal", n = 5, colors = c("red", "yellow", "blue"))

# Or with piping
scale3 <- my_data |> interpolate_palette("value", method = "equal", n = 5)

# Use in a layer
add_fill_layer(map, fill_color = scale1$expression)

# Extract legend information
labels <- get_legend_labels(scale1, format = "currency")
colors <- scale1$colors

}