Vertical line


from plotnine import (
    ggplot,
    aes,
    geom_point,
    geom_vline,
    facet_grid,
    labs,
    element_rect,
    theme,
    theme_matplotlib,
    theme_set,
)
from plotnine.data import mpg

# Set default theme
# matplotlib + the background of 538
theme_set(
    theme_matplotlib()
    + theme(
        plot_background=element_rect(fill="#F0F0F0"),
        panel_background=element_rect(fill="#F0F0F0"),
        panel_spacing=0.015,
        
    )
)

geom_vline() draws a vertical line, and is useful as a guide.

mpg.head()

	manufacturer	model	displ	year	cyl	trans	drv	cty	hwy	fl	class
0	audi	a4	1.8	1999	4	auto(l5)	f	18	29	p	compact
1	audi	a4	1.8	1999	4	manual(m5)	f	21	29	p	compact
2	audi	a4	2.0	2008	4	manual(m6)	f	20	31	p	compact
3	audi	a4	2.0	2008	4	auto(av)	f	21	30	p	compact
4	audi	a4	2.8	1999	6	auto(l5)	f	16	26	p	compact

It’s useful to use geom_vline() with some data, so we start with a basic scatter plot:

(
    ggplot(mpg, aes(x="displ", y="hwy"))
    + geom_point()
    + labs(x="displacement", y="horsepower")
)

Add a vertical line to the scatter plot:

(
    ggplot(mpg, aes(x="displ", y="hwy"))
    + geom_point()
    + geom_vline(xintercept=5)  # add one vertical line
    + labs(x="displacement", y="horsepower")
)

You can add many vertical lines:

(
    ggplot(mpg, aes(x="displ", y="hwy"))
    + geom_point()
    + geom_vline(xintercept=[4, 5, 7])  # add many vertical lines using a list
    + labs(x="displacement", y="horsepower")
)

(
    ggplot(mpg, aes(x="displ", y="hwy"))
    + geom_point()
    + geom_vline(
        xintercept=[4, 5, 7],
        colour=["red", "orange", "green"],  # add colour
        size=[1, 2, 3],  # set line thickness
        linetype="dotted",  # set line type
    )
    + labs(x="displacement", y="horsepower")
)

Add vertical lines to a facet plot:

Facets with a Vertical Line

# Gallery, lines
(
    ggplot(mpg, aes(x="displ", y="hwy"))
    + geom_point()
    + geom_vline(xintercept=5, color="brown", size=1)  # add a vertical line...
    + facet_grid("drv")  # ... to a facet plot
    + labs(x="displacement", y="horsepower")
)