Plot customizations for censored VPC

[certara-jcraig]

Adds the ability to customize colors in censoring (BLQ/ALQ) plots through new censoring.color and censoring.fill arguments in plot.tidyvpcobj(), addressing the feature request #67 to allow easier changing of BLQ/ALQ colour labels.

• Added censoring.color argument (named vector for line colors, default: c(observed = "black", simulated = "red"))
• Added censoring.fill argument (ribbon fill color, default: "red")
• Updated plot_censored() internal function to use these parameters instead of hardcoded values
• Updated /vignettes/tidyvpc_cont.Rmd adding "Customizing Censoring Plot Colors" subsection with examples

Usage examples

Basic color customization via new arguments

library(tidyvpc)

vpc <- observed(obs_data, x = TIME, y = DV) %>%
  simulated(sim_data, y = DV) %>%
  censoring(blq = DV < 50, lloq = 50) %>%
  binning(bin = "jenks", nbins = 5) %>%
  vpcstats()

# Customize censoring plot colors directly
plot(vpc, censoring.type = "blq",
     censoring.color = c(observed = "blue", simulated = "orange"),
     censoring.fill = "orange")

For users who need full ggplot2 control, use censoring.output = "list" to return individual ggplot objects that can be modified:

# Get plots as a list instead of arranged grid
plot_list <- plot(vpc, censoring.type = "blq", censoring.output = "list")

# plot_list[[1]] = main VPC plot
# plot_list[[2]] = BLQ percentage plot

# Customize the BLQ plot with ggplot2 functions
plot_list[[2]] + 

  ggplot2::scale_colour_manual(
    values = c(observed = "darkgreen", simulated = "purple")
  ) +
  ggplot2::labs(
    colour = "Custom Legend Title",
    title = "Percentage Below Limit of Quantification"
  ) +
  ggplot2::theme_minimal()

# Combine plots manually using patchwork or cowplot
library(patchwork)
plot_list[[1]] / plot_list[[2]]