The provided code defines a new stat called DensityTern2 which is used to create a ternary density plot. The stat takes in several parameters, including the data, colors, and breaks.

Here’s a breakdown of the code:

1. Defining the Stat: The first section of the code defines the DensityTern2 stat using R’s grammar-based system for creating graphics.

StatDensityTern2 <- function(data, aes_object, params = list()) { # Implementation of the stat }

2.  **Implementation**: Inside the `StatDensityTern2` function, we implement the logic to create a ternary density plot. This involves several steps:
    *   We first calculate the compositions of each data point using `acomp`.
    *   Then, we assign non-zero values for each component and remove missing values.
    *   We define the bandwidth for the kernel density estimation using `estimateBandwidth` if the base is "ilr".
    *   Next, we perform the KDE on the data points using `kde2d.weighted`.
    *   We then create a dataframe with the expanded grid of x and y values, along with the corresponding densities.
3.  **Using the Stat**: In the example code, we use the `DensityTern2` stat to create a ternary density plot for the given data.
    ```r
  df = data.frame(expand.grid(x = dens$x, y = dens$y), 
                  z = as.vector(dens$z) * nrow(data), 
                  group = data$group[1])

  if (contour) {
    df = StatContour$compute_panel(df, scales, bins = bins, 
                                  binwidth = binwidth, breaks = breaks)
  } else {
    # ... other code to handle non-contour plots ...
  }

4. Customizing the Plot: We customize the plot by adding a grey fill color and controlling the alpha value of each polygon.

Here’s the complete code:

set.seed(1234)

# example data
df <- data.frame(X = c(runif(150, 0.7, 1), runif(50, 0, 0.3)),
                 Y = c(runif(150, 0, 0.3), runif(50, 0, 0.3)),
                 Z = c(runif(150, 0, 0.5), runif(50, 0.5, 1)),
                 D = c(rep("A", 150), rep("B", 50)))

ggtern(df, aes(x = X, y = Y, z = Z, color = D)) +
  geom_polygon(aes(alpha = ..level.., fill = D),
               stat = "DensityTern2",
               breaks = seq(10, 150, by = 10),
               color = "grey") +
  geom_point(alpha = 0.5) +
  scale_colour_manual(values = c("tomato3", "turquoise4"))

This code creates a ternary density plot with the specified data and customizations. The DensityTern2 stat provides an efficient way to visualize ternary data, allowing for easy control over the appearance of the plot.

Last modified on 2024-06-29