Creating a custom Stat object in ggplot2

Question

I'd like to create a custom Stat object for ggplot2. (Specifically I'd like to create a smoother that works differently than the ones stat_smooth allows- for instance, without a y~x modeling function- but there are other custom Stats I'd like to create even if there were a workaround for my specific case).

I found this suggested solution from Hadley Wickham:

StatExpo <- proto(Stat, {
  objname <- "expo"
  desc <- "Exponential smoothing"
  default_geom <- function(.) GeomLine

  calculate_groups <- function(., data, scales, variable="x", ...) {
    data$y <- HoltWinters(data$x, ...)
  }
})
stat_expo <- StatExpo$new

However, when I try it I get:

Error in proto(Stat, { : object 'Stat' not found

Upon looking around the ggplot code, I found where Stat is defined. However, the Stat object is, as far as I can tell, never exported from ggplot2.

I could write my new stat object within the ggplot2/R folder and then reinstall the package, but obviously this would be cumbersome and make the solution very difficult to share with others. How can I create a custom Stat object outside of the ggplot namespace?

@baptiste Nope, Error: 'Stat' is not an exported object from 'namespace:ggplot2'. Does it work for you? — David Robinson
– David Robinson, Commented Aug 7, 2013 at 16:34
@baptiste Ah! I misread. That works; please post it as an answer. — David Robinson
– David Robinson, Commented Aug 7, 2013 at 16:39

baptiste · Accepted Answer · 2013-08-07 16:40:56Z

5

ggplot2:::Stat can be used to access the non-exported object.

answered Aug 7, 2013 at 16:40

baptiste

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1 Comment

Frank Harrell Over a year ago

Needing ::: will prevent a user-defined function from being included in a package to be submitted to CRAN, unfortunately. CRAN checks do not allow :::.

Nicholas Hamilton · Accepted Answer · 2015-07-31 06:20:18Z

1

getFromNamespace('Stat','ggplot2')

answered Jul 31, 2015 at 6:20

Nicholas Hamilton

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