How to add a diagonal line to a plot?

Question

I want to add a diagonal line to the plot. It is not a linear regression line. I just want a diagnol line. Can anyone help me with this? Thanks a lot!

Have a look at `abline(...)`. – jlhoward Dec 14 '14 at 01:13 — jlhoward, Dec 14 '14 at 01:13
or `geom_abline` if you are using ggplot – rawr Dec 14 '14 at 01:15 — rawr, Dec 14 '14 at 01:15

score 15 · Answer 1 · answered Mar 29 '17 at 14:39

15

If you want to add the 1:1 diagonal line:

qplot(1,1) + geom_abline(intercept = 0, slope = 1)

answered Mar 29 '17 at 14:39

Lennert

964
10
16

score 14 · Answer 2 · answered Apr 24 '19 at 08:19

You could use abline()

abline(coef = c(0,1))

this gives you a line from intercept 0 with slope 1 in an existing plot.

If you want the line to be diagonal to any plot just set the intercept to the lower left corner and the slope to the ratio of increase between the two axis.

kilojoules · Answer 3 · 2014-12-14T05:51:27.750

10

lines(x = c(0,100), y = c(0,100))

edited Dec 14 '14 at 05:51

answered Dec 14 '14 at 01:23

kilojoules

9,768
18
77
149

score 2 · Answer 4 · answered May 05 '20 at 15:22

Maybe this is a bit late however, I want to share my answer with you -maybe useful. First, define a panel function and within that define your abline parameters; like below:

require(hexbin)
y=runif(100)
x=runif(100)

panel <- function(x,y, ...){
panel.xyplot(x, y, ...)
panel.abline(0,1, col="red", size = 0.25, lwd = 2)
}

You can customize parameters based on your use-case.

Then you can add "panel" function into your plotting library i.e., ggplot or hexbin plot family. Here I use hexbinplot function which is a very nice function for visualization:

hexbinplot(x ~ y, panel = panel)

Below is how it looks like (remember you can make it much nicer by customizing graphical elements).

score 0 · Answer 5 · answered Dec 14 '14 at 02:06

If you don't want your line to extend through the entire plot range, or if you want to add arbitrary line segments, use segments. For example, the following code will draw a square:

plot.new()
plot.window(xlim = c(0, 3), ylim = c(0, 3))
segments(x0=c(1,1,2,2), x1=c(1,2,2,1), y0=c(1,2,2,1), y1=c(2,2,1,1))

score 0 · Answer 6 · answered Dec 14 '14 at 13:43

0

this adds a diagonal line to a ggplot,

qplot(1,1) + annotation_custom(linesGrob(c(0,1), c(0,1)))

or equivalently,

qplot(1,1) + annotate("segment", x=-Inf, xend=Inf,y=-Inf, yend=Inf)

answered Dec 14 '14 at 13:43

baptiste

75,767
19
198
294

score 0 · Answer 7 · answered May 31 '18 at 11:48

0

A diagonal one, from 0 to 100, for example to show actual vs predicted values: abline=c(0,1)

answered May 31 '18 at 11:48

Chema_arguez

57
8

score -2 · Answer 8 · edited Mar 01 '18 at 15:57

-2

To add a line, for example, from x=-3, y=-3 to x=3, y=3:

segments(-3,-3,3,3)

edited Mar 01 '18 at 15:57

Matin Kh

5,192
6
53
77

answered Mar 01 '18 at 15:14

Kimmo

1

How to add a diagonal line to a plot?

8 Answers8