First steps 3: Adding legends, text, and annotations¶
In the previous first steps guide, you generated different glyphs and defined their appearance.
In this section, you will add and style a legend and a headline. You will also add additional information to your plot by including annotations.
Adding and styling a legend¶
Bokeh automatically adds a legend to your plot if you include the
legend_label
attribute when calling the renderer function. For example:
p.circle(x, y3, legend_label="Objects")
This adds a legend with the entry “Objects” to your plot.
Use the properties of the Legend
object to customize the legend. For example:
from bokeh.plotting import figure, show
# prepare some data
x = [1, 2, 3, 4, 5]
y1 = [4, 5, 5, 7, 2]
y2 = [2, 3, 4, 5, 6]
# create a new plot
p = figure(title="Legend example")
# add circle renderer with legend_label arguments
line = p.line(x, y1, legend_label="Temp.", line_color="blue", line_width=2)
circle = p.circle(
x,
y2,
legend_label="Objects",
fill_color="red",
fill_alpha=0.5,
line_color="blue",
size=80,
)
# display legend in top left corner (default is top right corner)
p.legend.location = "top_left"
# add a title to your legend
p.legend.title = "Obervations"
# change appearance of legend text
p.legend.label_text_font = "times"
p.legend.label_text_font_style = "italic"
p.legend.label_text_color = "navy"
# change border and background of legend
p.legend.border_line_width = 3
p.legend.border_line_color = "navy"
p.legend.border_line_alpha = 0.8
p.legend.background_fill_color = "navy"
p.legend.background_fill_alpha = 0.2
# show the results
show(p)
See also
To learn more about legends, see Legends in the
annotations section and Styling legends in the styling
section of the user guide. The entry Legend
in the reference guide
contains a list of all available attributes for legends.
See interactive legends in the user guide to learn about using legends to hide or mute glyphs in a plot.
Customizing headlines¶
Most of the examples so far have included a headline. You did this by passing
the title
argument to the figure()
function:
p = figure(title="Headline example")
There are various ways to style the text for your headline. For example:
from bokeh.plotting import figure, show
# prepare some data
x = [1, 2, 3, 4, 5]
y = [6, 7, 2, 4, 5]
# create new plot
p = figure(title="Headline example")
# add line renderer with a legend
p.line(x, y, legend_label="Temp.", line_width=2)
# change headline location to the left
p.title_location = "left"
# change headline text
p.title.text = "Changing headline text example"
# style the headline
p.title.text_font_size = "25px"
p.title.align = "right"
p.title.background_fill_color = "darkgrey"
p.title.text_color = "white"
# show the results
show(p)
Using annotations¶
Annotations are visual elements that you add to your plot to make it easier to read. For more information on the various kinds of annotations, see Adding annotations in the user guide.
One example are box annotations. You can use box annotations to highlight certain areas of your plot:
To add box annotations to your plot, you first need to import the
BoxAnnotation
class from bokeh.models:
from bokeh.models import BoxAnnotation
Next, create the BoxAnnotation
objects. If you do not pass a value for
bottom
or top
, Bokeh automatically extends the box’s dimension to the
edges of the plot:
low_box = BoxAnnotation(top=80, fill_alpha=0.1, fill_color='red')
mid_box = BoxAnnotation(bottom=80, top=180, fill_alpha=0.1, fill_color='green')
high_box = BoxAnnotation(bottom=180, fill_alpha=0.1, fill_color='red')
Finally, you need to add the BoxAnnotation
objects to your existing figure.
Use the add_layout()
method to add your boxes:
p.add_layout(low_box)
p.add_layout(mid_box)
p.add_layout(high_box)
This is what the finished code looks like:
import random
from bokeh.models import BoxAnnotation
from bokeh.plotting import figure, show
# generate some data (1-50 for x, random values for y)
x = list(range(0, 51))
y = random.sample(range(0, 100), 51)
# create new plot
p = figure(title="Box annotation example")
# add line renderer
line = p.line(x, y, line_color="blue", line_width=2)
# add box annotations
low_box = BoxAnnotation(top=20, fill_alpha=0.1, fill_color="red")
mid_box = BoxAnnotation(bottom=20, top=80, fill_alpha=0.1, fill_color="green")
high_box = BoxAnnotation(bottom=80, fill_alpha=0.1, fill_color="red")
# add boxes to existing figure
p.add_layout(low_box)
p.add_layout(mid_box)
p.add_layout(high_box)
# show the results
show(p)
See also
To find out more about the different kinds of annotations in Bokeh, see Adding annotations in the user guide.