Description
Every time I encounter a question like #3497, I wonder why ggplot2 doesn't have a Stat that simply applies a function by group. Though, in terms of the computational efficiency, it's generally better to have a summarised version of the data before entering ggplot2, it would be handy if we can summarise in ggplot2 especially when we generate plots one after another with different groupings.
I believe StatSummary could have been implemented to be able to summarise data with other groupings than c("group", "x") because the code following seems very general one:
Lines 163 to 169 in b842024
But, as the current make_summary_fun() expects a function that takes a vector, not a data.frame, it would be difficult to expand StatSummary to accept a function that summarises both x and y. So, to satisfy the need, I feel it might be nice to have some simple geom like below.
I don't see reasons why we shouldn't implement such a Stat. Am I missing something...?
library(ggplot2)
stat_summary_by_group <- function(mapping = NULL, data = NULL,
geom = "pointrange", position = "identity",
...,
fun.data = NULL,
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE) {
layer(
data = data,
mapping = mapping,
stat = StatSummaryByGroup,
geom = geom,
position = position,
show.legend = show.legend,
inherit.aes = inherit.aes,
params = list(
fun.data = fun.data,
na.rm = na.rm,
...
)
)
}
StatSummaryByGroup <- ggproto("StatSummaryByGroup", Stat,
compute_group = function(data, scales, fun.data = NULL, na.rm = FALSE) {
summary <- fun.data(data)
unique <- ggplot2:::dapply(data, c("group"), ggplot2:::uniquecols)
unique[names(summary)] <- summary
unique
}
)
d <- data.frame(x = c(1:5, 3:7), y = 1:10, g = rep(c("a", "b"), each = 5), stringsAsFactors = FALSE)
f <- function(d) {
data.frame(x = min(d$x), xend = max(d$x), y = mean(d$y), yend = mean(d$y))
}
ggplot(d) +
geom_point(aes(x, y, colour = g)) +
stat_summary_by_group(fun.data = f, aes(x, y, xend = stat(xend), yend = stat(yend)), geom = "segment") +
facet_grid(cols = vars(g))
Created on 2019-08-24 by the reprex package (v0.3.0)