ggplot with arrows
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-bounces at r-project.org> On Behalf Of Thomas Subia via R-help
Sent: Friday, August 1, 2025 10:31 AM
To: r-help at 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