Generate Variogram Plot

Creates a variogram plot showing the spatial dependence structure of the data. The plot includes both the empirical variogram points and the fitted theoretical variogram line. The empirical variogram points show the actual semivariance values at different distances, while the red line shows the fitted exponential variogram model.

Usage

generate_variogram_plot(
  age_param_data,
  fit_vario,
  country_code,
  scale_outcome = "log_scale",
  output_dir,
  width = 12,
  height = 9,
  png_resolution = 300
)

Arguments

age_param_data

Data frame containing the age parameter data. Must include columns 'web_x' and 'web_y' for spatial coordinates and the response variable specified in scale_outcome.

fit_vario

Fitted variogram object from automap package. Should contain components $psill (partial sill) and $range (range parameter) for the exponential variogram model.

country_code

Character string of the country code (e.g. "TZA") used for plot title and output filename.

scale_outcome

Character string specifying the column name for the scale parameter response variable (default: "log_scale"). This is the variable for which the variogram is computed.

output_dir

Character string specifying the directory path where the plot will be saved as a PNG file.

width

Plot width in pixels (default: 2000). Controls the output image width.

height

Plot height in pixels (default: 1500). Controls the output image height.

png_resolution

PNG resolution in DPI (dots per inch, default: 300). Higher values create larger, higher quality images.

Value

Invisibly returns the ggplot object containing the variogram plot. The plot is also saved as a PNG file in the specified output directory.

Details

The function creates a variogram plot with the following elements: - Points showing empirical semivariance values at different distances - A red line showing the fitted exponential variogram model - Clear axis labels and title - Comma-formatted distance values on x-axis - Clean theme with black and white style

The output filename is constructed as lowercase country code + "_variogram.png"

Examples

# \donttest{
set.seed(123)  # For reproducibility
age_param_data <- data.frame(
  country = rep("TZA", 100),
  web_x = runif(100, 0, 100),
  web_y = runif(100, 0, 100),
  log_scale = rnorm(100, mean = 5, sd = 2)
)

# Create a dummy fitted variogram object
fit_vario <- list(
  psill = c(0.1, 0.5),
  range = c(0, 50)
)

vario_plot <- generate_variogram_plot(
   age_param_data = age_param_data,
   fit_vario = fit_vario,
   country_code = "TZA",
   output_dir = file.path(tempdir()))
#> ✔ Variogram saved to /tmp/RtmpioKZmp/tza_variogram.png
# }