The “geom_tile” Function in R

• Package: ggplot2

• Purpose: To create a heatmap or a tile plot by filling rectangles with colors based on a continuous variable or specified values.

• General Class: Data Visualization

• Required Argument(s):

• mapping: Specifies the aesthetic mapping.

• Notable Optional Arguments:

• width, height: Controls the width and height of the tiles.

• fill: Sets the color of the tiles.

• color: Sets the color of the border around the tiles.

• linetype: Specifies the type of line for the tile borders.

• Example (with Explanation):

• # Example Data
  matrix_data <- matrix(1:9, ncol = 3)
  rownames(matrix_data) <- c("Row1", "Row2", "Row3")
  colnames(matrix_data) <- c("Col1", "Col2", "Col3")
  
  # Load necessary packages
  library(ggplot2)
  library(reshape2)
  
  # Melt the matrix
  melted_data <- melt(matrix_data)
  
  # Basic Tile Plot
  ggplot(melted_data, aes(x = Var2, y = Var1, fill = value)) +
  geom_tile(color = "white") +
  scale_fill_gradient(low = "lightblue", high = "darkblue") +
  labs(title = "Basic Tile Plot", x = "Columns", y = "Rows")

• In this example, the geom_tile function is used to create a basic tile plot. The matrix data is melted into a long format using the melt function from the reshape2 package, and the resulting data frame is used to create the plot. The Var1 and Var2 are mapped to the x and y-axis, and the value variable is used to fill the tiles with colors. The scale_fill_gradient function is employed to define a gradient color scale for the tiles.