Customize Legend Appearance

import io
import requests

import pandas as pd
from PIL import Image

from lets_plot import *

LetsPlot.setup_html()

response = requests.get("https://raw.githubusercontent.com/JetBrains/lets-plot-docs/master/source/examples/cookbook/images/theme_legend_scheme.png", timeout=5*60)
Image.open(io.BytesIO(response.content))

df = pd.read_csv("https://raw.githubusercontent.com/JetBrains/lets-plot-docs/master/data/mpg.csv")
print(df.shape)
df.head()

(234, 12)

	Unnamed: 0	manufacturer	model	displ	year	cyl	trans	drv	cty	hwy	fl	class
0	1	audi	a4	1.8	1999	4	auto(l5)	f	18	29	p	compact
1	2	audi	a4	1.8	1999	4	manual(m5)	f	21	29	p	compact
2	3	audi	a4	2.0	2008	4	manual(m6)	f	20	31	p	compact
3	4	audi	a4	2.0	2008	4	auto(av)	f	21	30	p	compact
4	5	audi	a4	2.8	1999	6	auto(l5)	f	16	26	p	compact

Legend Position

Parameters to customize the legend position and justification:

• legend_position - the position of legends;

• legend_justification - anchor point for positioning legend;

• legend_direction - layout of items in legends.

p1 = ggplot(df, aes("displ", "hwy")) + geom_point(aes(color="cty", shape="drv"), size=5)
p1

# Draw legend below the plot area
p1 + theme(legend_position='bottom')

# Specify position, justification and orientation
p1 + theme(legend_position=[1, 1], legend_justification=[1, 1], legend_direction='horizontal')

Legend Spacing and Margins

Parameters to customize the legend spacing and margins:

• legend_box - arrangement of multiple legends (“horizontal” or “vertical”);

• legend_box_just - justification of each legend within the overall bounding box (“top”, “bottom”, “left”, “right”, “center”);

• legend_box_spacing - spacing between plotting area and legend box;

• legend_margin - margin around each legend;

• legend_spacing - spacing between legends, legend_spacing_x/legend_spacing_y - in the horizontal/vertical direction.

p2 = ggplot(df, aes('displ', 'cty')) + \
    geom_point(aes(fill='drv', size='hwy'), shape=21) + \
    scale_size(range=[1, 10], breaks=[15, 30, 40]) + \
    theme(legend_position='bottom', legend_background=element_rect(size=1))
p2

# legend_margin
p2 + theme(legend_margin=[10, 20])

# legend_box
p2 + theme(legend_box='horizontal')

# legend_box_just
p2 + theme(legend_box_just='center')

# legend_box_spacing
p2 + theme(legend_box='horizontal',  legend_box_spacing=50)

# legend_spacing
p2 + theme(legend_box='horizontal', legend_spacing_x=50)

Legend Key Parameters

Parameters to customize the legend key:

• legend_key - background underneath legend keys, set with element_rect();

• legend_key_size - size of legend keys;

• legend_key_width - key background width;

• legend_key_height - key background height;

• legend_key_spacing - spacing between legend keys;

• legend_key_spacing_x - spacing in the horizontal direction;

• legend_key_spacing_y - spacing in the vertical direction.

p3 = ggplot(df, aes(x='hwy')) + \
    geom_dotplot(aes(fill='class'), color='pen') + \
    theme(legend_background=element_rect(size=0.5))
p3

Add background underneath legend keys:

p4 = p3 + theme(legend_key=element_rect(fill='#efedf5', color='#756bb1'))
p4

Change size of legend keys:

p4 + theme(legend_key_size=30)

p5 = p4 + theme(legend_key_width=80, legend_key_height=20)
p5

Add spacing between legend keys:

p5 + theme(legend_key_spacing_y=10)