double dots in a ggplot

by

Unlike many other languages, in R, the dot is perfectly valid in identifiers. In this case, ..count.. is an identifier. However, there is special code in ggplot2 to detect this pattern, and to strip the dots. It feels unlikely that real code would use identifiers formatted like that, and so this is a neat way to distinguish between defined and calculated aesthetics.

The relevant code is at the end of layer.r:

# Determine if aesthetic is calculated
is_calculated_aes <- function(aesthetics) {
  match <- "\\.\\.([a-zA-z._]+)\\.\\."
  stats <- rep(FALSE, length(aesthetics))
  grepl(match, sapply(aesthetics, deparse))
}

# Strip dots from expressions
strip_dots <- function(aesthetics) {
  match <- "\\.\\.([a-zA-z._]+)\\.\\."
  strings <- lapply(aesthetics, deparse)
  strings <- lapply(strings, gsub, pattern = match, replacement = "\\1")
  lapply(strings, function(x) parse(text = x)[[1]]) 
}

It is used further up above in the map_statistic function. If a calculated aesthetic is present, another data frame (one that contains e.g. the count column) is used for the plot.

The single dot . is just another identifier, defined in the plyr package. As you can see, it is a function.

More Related Contents:

  1. Force the origin to start at 0
  2. Create stacked barplot where each stack is scaled to sum to 100%
  3. Inserting an image to ggplot2
  4. How to set multiple legends / scales for the same aesthetic in ggplot2?
  5. Addressing x and y in aes by variable number
  6. customize ggplot2 axis labels with different colors
  7. Adding space between bars in ggplot2
  8. ggplot2: change order of display of a factor variable on an axis
  9. Center x and y axis with ggplot2
  10. Using `geom_line()` with X axis being factors
  11. Filling area under curve based on value
  12. Align plot areas in ggplot
  13. Save plot with a given aspect ratio
  14. Getting a stacked area plot in R
  15. geom_text how to position the text on bar as I want?
  16. How to extract the fill colours from a ggplot object?
  17. ggplot2 multiple scales/legends per aesthetic, revisited [duplicate]
  18. Force ggplot legend to show all categories when no values are present [duplicate]
  19. modifying ggplot objects after creation
  20. Greek letters, symbols, and line breaks inside a ggplot legend label
  21. how do you order Months in ggplot
  22. Layered axes in ggplot?
  23. How to specify columns in facet_grid OR how to change labels in facet_wrap
  24. Specify height and width of ggplot graph in Rmarkdown knitr output
  25. How to get geom_vline to honor facet_wrap?
  26. R – ggplot line color (using geom_line) doesn’t change
  27. When does the argument go inside or outside aes()?
  28. R ggplot ordering bars within groups
  29. ggplot for loop outputs all the same graph
  30. group by two columns in ggplot2

Leave a Comment