On 8/1/2025 3:43 PM, Ebert,Timothy Aaron wrote:
I would save the graph as a PowerPoint object and then edit it in PowerPoint.
library(ggplot2)
library(grid)
library(officer)
library(rvg)
x <- seq(-5, 5, length.out = 100)
y <- x^2
data <- data.frame(x, y)
plot <- ggplot(data, aes(x, y)) +
   geom_path(color = "blue", linewidth = 1.25) +
   geom_segment(
     aes(x = x[1], y = y[1], xend = x[100], yend = y[100]),
     arrow = arrow(angle = 20, type = "closed", ends = "both", length = unit(0.2, 
"inches")),
     color = "red"
   ) +
   theme_linedraw()
doc <- read_pptx()
doc <- add_slide(doc, layout = "Title and Content", master = "Office Theme")
doc <- ph_with(doc, dml(ggobj = plot), location = ph_location_fullsize())
print(doc, target = "quadratic_with_arrows.pptx")

If I remember I think you have to ungroup it in PowerPoint and then all 
elements become editable. The general approach can be done with other file 
formats/programs, not just PowerPoint.
Tim

-----Original Message-----
From: R-help <r-help-boun...@r-project.org> On Behalf Of Thomas Subia via R-help
Sent: Friday, August 1, 2025 10:31 AM
To: r-help@r-project.org
Subject: [R] ggplot with arrows

[External Email]

Consider:

x <- seq(-5,5,length.out = 100)
y <- x^2
data <- data.frame(x,y)
library(ggplot2)
ggplot(data,aes(x,y))+
   stat_function(
     fun = function(x) x^2,
     color = "blue", linewidth = 1.25
   ) +
   theme_linedraw()
I'd like to add an arrow to the ends of curve to illustrate the curve continues 
indefinitely in that direction, ChatGPT suggests using geom_segment or 
geom_link but there has an easier way to do this.

Any suggestions would be appreciated.


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Hello,

First of all, according to the documentation ?stat_function, section Arguments,


data    
Ignored by stat_function(), do not use.


As for the arrows, first get the equations of the lines tangent to the end points of the parabola,

y = -10*x - 25
y = 10*x - 25

then compute segments' end points and plot.


f <- function(x, b = -25, m) m*x + b
arrow_data <- data.frame(
  id = c("n", "p"),
  x = c(-5, 5),
  y = f(c(-5, 5), m = c(-10, 10)),
  xend = c(-6, 6),
  yend = f(c(-6, 6), m = c(-10, 10))
)

ggplot() +
  stat_function(
    fun = function(x) x^2,
    color = "blue", linewidth = 1.25,
    xlim = c(-5, 5)
  ) +
  geom_segment(
    data = arrow_data,
    mapping = aes(x = x, y = y, xend = xend, yend = yend, group = id),
    arrow = arrow(length = unit(0.5, "cm")),
    linewidth = 1.25,
    linetype = "dashed",
    inherit.aes = FALSE
  ) +
  theme_linedraw()



Remove linetype and add color if you want.

Hope this helps,

Rui Barradas

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