Python Bokeh is a Data Visualization library that provides interactive charts and plots. Bokeh renders its plots using HTML and JavaScript that uses modern web browsers for presenting elegant, concise construction of novel graphics with high-level interactivity.
Features of Bokeh:
This tutorial aims at providing insight to Bokeh using well-explained concepts and examples with the help of a huge dataset. So let's dive deep into the Bokeh and learn all it from basic to advance.
Table Of Content
Installation
- Installation
- Bokeh Interfaces – Basic Concepts of Bokeh
- Getting Started
- Annotations and Legends
- Plotting Different Types of Plots
- Creating Different Shapes
- Plotting Multiple Plots
- Interactive Data Visualization
- Creating Different Types of Glyphs
- Visualizing Different Types of Data
- More Topics on Bokeh
Bokeh is supported by CPython 3.6 and older with both standard distribution and anaconda distribution. Bokeh package has the following dependencies.
1. Required Dependencies
2. Optional Dependencies
Bokeh can be installed using both conda package manager and pip. To install it using conda type the below command in the terminal.
conda install bokeh
This will install all the dependencies. If all the dependencies are installed then you can install the bokeh from PyPI using pip. Type the below command in the terminal.
pip install bokeh
Refer to the below article to get detailed information about the installation of Bokeh.
Bokeh Interfaces - Basic Concepts of BokehBokeh is simple to use as it provides a simple interface to the data scientists who do not want to be distracted by its implementation and also provides a detailed interface to developers and software engineers who may want more control over the Bokeh to create more sophisticated features. To do this Bokeh follows the layered approach.
Bokeh.modelsThis class is the Python Library for Bokeh that contains model classes that handle the JSON data created by Bokeh's JavaScript library (BokehJS). Most of the models are very basic consisting of very few attributes or no methods.
bokeh.plottingThis is the mid-level interface that provides Matplotlib or MATLAB like features for plotting. It deals with the data that is to be plotted and creating the valid axes, grids, and tools. The main class of this interface is the Figure class.
Getting StartedAfter the installation and learning about the basic concepts of Bokeh let's create a simple plot.
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title = "Bokeh Line Graph")
# the points to be plotted
x = [1, 2, 3, 4, 5]
y = [5, 4, 3, 2, 1]
# plotting the line graph
graph.line(x, y)
# displaying the model
show(graph)
Output:
In the above example, we have created a simple Plot with the Title as Bokeh Line Graph. If you are using Jupyter then the output will be created in a new tab in the browser.
Annotations and LegendsAnnotations are the supplemental information such as titles, legends, arrows, etc that can be added to the graphs. In the above example, we have already seen how to add the titles to the graph. In this section, we will see about the legends.
Adding legends to your figures can help to properly describe and define them. Hence, giving more clarity. Legends in Bokeh are simple to implement. They can be basic, automatically grouped, manually mentioned, explicitly indexed, and also interactive.
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title="Bokeh Line Graph")
# the points to be plotted
x = [1, 2, 3, 4, 5]
y = [5, 4, 3, 2, 1]
# plotting the 1st line graph
graph.line(x, x, legend_label="Line 1")
# plotting the 2nd line graph with a
# different color
graph.line(y, x, legend_label="Line 2",
line_color="green")
# displaying the model
show(graph)
Output:
In the above example, we have plotted two different lines with a legend that simply states that which is line 1 and which is line 2. The color in the legends is also differentiated by the color.
Refer to the below articles to get detailed information about the annotations and legends
Customizing LegendsLegends in Bokeh can be customized using the following properties.
Property Description legend.label_text_font change default label font to specified font name legend.label_text_font_size font size in points legend.location set the label at specified location. legend.title set title for legend label legend.orientation set to horizontal (default) or vertical legend.clicking_policy specify what should happen when legend is clickedExample:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title="Bokeh Line Graph")
# the points to be plotted
x = [1, 2, 3, 4, 5]
y = [5, 4, 3, 2, 1]
# plotting the 1st line graph
graph.line(x, x, legend_label="Line 1")
# plotting the 2nd line graph with a
# different color
graph.line(y, x, legend_label="Line 2",
line_color="green")
graph.legend.title = "Title of the legend"
graph.legend.location ="top_left"
graph.legend.label_text_font_size = "17pt"
# displaying the model
show(graph)
Output:
Plotting Different Types of PlotsGlyphs in Bokeh terminology means the basic building blocks of the Bokeh plots such as lines, rectangles, squares, etc. Bokeh plots are created using the bokeh.plotting interface which uses a default set of tools and styles.
Line PlotLine charts are used to represent the relation between two data X and Y on a different axis. A line plot can be created using the line() method of the plotting module.
Syntax:
line(parameters)
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title = "Bokeh Line Graph")
# the points to be plotted
x = [1, 2, 3, 4, 5]
y = [5, 4, 3, 2, 1]
# plotting the line graph
graph.line(x, y)
# displaying the model
show(graph)
Output:
Refer to the below articles to get detailed information about the line plots.
Bar PlotBar plot or Bar chart is a graph that represents the category of data with rectangular bars with lengths and heights that is proportional to the values which they represent. It can be of two types horizontal bars and vertical bars. Each can be created using the hbar() and vbar() functions of the plotting interface respectively.
Syntax:
hbar(parameters)
vbar(parameters)
Example 1: Creating horizontal bars.
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title = "Bokeh Bar Graph")
# the points to be plotted
x = [1, 2, 3, 4, 5]
y = [1, 2, 3, 4, 5]
# height / thickness of the plot
height = 0.5
# plotting the bar graph
graph.hbar(x, right = y, height = height)
# displaying the model
show(graph)
Output:
Example 2: Creating the vertical bars
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title = "Bokeh Bar Graph")
# the points to be plotted
x = [1, 2, 3, 4, 5]
y = [1, 2, 3, 4, 5]
# height / thickness of the plot
width = 0.5
# plotting the bar graph
graph.vbar(x, top = y, width = width)
# displaying the model
show(graph)
Output:
Refer to the below articles to get detailed information about the bar charts.
Scatter PlotA scatter plot is a set of dotted points to represent individual pieces of data in the horizontal and vertical axis. A graph in which the values of two variables are plotted along X-axis and Y-axis, the pattern of the resulting points reveals a correlation between them. It can be plotted using the scatter() method of the plotting module.
Syntax:
scatter(parameters)
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
from bokeh.palettes import magma
import random
# instantiating the figure object
graph = figure(title = "Bokeh Scatter Graph")
# points to be plotted
x = [n for n in range(256)]
y = [random.random() + 1 for n in range(256)]
# plotting the graph
graph.scatter(x, y)
# displaying the model
show(graph)
Output:
Refer to the below articles to get detailed information about the scatter plots.
Patch PlotPatch Plot shades a region of area to show a group having same properties. It can be created using the patch() method of the plotting module.
Syntax:
patch(parameters)
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
from bokeh.palettes import magma
import random
# instantiating the figure object
graph = figure(title = "Bokeh Patch Plo")
# points to be plotted
x = [n for n in range(256)]
y = [random.random() + 1 for n in range(256)]
# plotting the graph
graph.patch(x, y)
# displaying the model
show(graph)
Output:
Refer to the below articles to get detailed information about the Patch Plot.
Area PlotArea plots are defined as the filled regions between two series that share a common areas. Bokeh Figure class has two methods which are - varea(), harea()
Syntax:
varea(x, y1, y2, **kwargs)
harea(x1, x2, y, **kwargs)
Example 1: Creating vertical area plot
Python
# Implementation of bokeh function
import numpy as np
from bokeh.plotting import figure, output_file, show
x = [1, 2, 3, 4, 5]
y1 = [2, 4, 5, 2, 4]
y2 = [1, 2, 2, 3, 6]
p = figure(plot_width=300, plot_height=300)
# area plot
p.varea(x=x, y1=y1, y2=y2,fill_color="green")
show(p)
Output:
Example 2: Creating horizontal area plot
Python3
# Implementation of bokeh function
import numpy as np
from bokeh.plotting import figure, output_file, show
y = [1, 2, 3, 4, 5]
x1 = [2, 4, 5, 2, 4]
x2 = [1, 2, 2, 3, 6]
p = figure(plot_width=300, plot_height=300)
# area plot
p.harea(x1=x1, x2=x2, y=y,fill_color="green")
show(p)
Output:
Refer to the below articles to get detailed information about the area charts
Pie ChartBokeh Does not provide a direct method to plot the Pie Chart. It can be created using the wedge() method. In the wedge() function, the primary parameters are the x and y coordinates of the wedge, the radius, the start_angle and the end_angle of the wedge. In order to plot the wedges in such a way that they look like a pie chart, the x, y, and radius parameters of all the wedges will be the same. We will only adjust the start_angle and the end_angle.
Syntax:
wedge(parameters)
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title = "Bokeh Wedge Graph")
# the points to be plotted
x = 0
y = 0
# radius of the wedge
radius = 15
# start angle of the wedge
start_angle = 1
# end angle of the wedge
end_angle = 2
# plotting the graph
graph.wedge(x, y, radius = radius,
start_angle = start_angle,
end_angle = end_angle)
# displaying the model
show(graph)
Output:
Refer to the below articles to get detailed information about the pie charts.
Creating Different ShapesThe Figure class in Bokeh allows us create vectorised glyphs of different shapes such as circle, rectangle, oval, polygon, etc. Let's discuss them in detail.
CircleBokeh Figure class following methods to draw circle glyphs which are given below:
Example:
Python3
import numpy as np
from bokeh.plotting import figure, output_file, show
# creating the figure object
plot = figure(plot_width = 300, plot_height = 300)
plot.circle(x = [1, 2, 3], y = [3, 7, 5], size = 20)
show(plot)
Output:
Refer to the below articles to get detailed information about the circle glyphs
Ovaloval() method can be used to plot ovals on the graph.
Syntax:
oval(parameters)
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title = "Bokeh Oval Graph")
# the points to be plotted
x = [1, 2, 3, 4, 5]
y = [i * 2 for i in x]
# plotting the graph
graph.oval(x, y,
height = 0.5,
width = 1)
# displaying the model
show(graph)
Output:
Refer o the below articles to get detailed information about the oval glyphs.
TriangleTriangle can be created using the triangle() method.
Syntax:
triangle(parameters)
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title = "Bokeh Triangle Graph")
# the points to be plotted
x = 1
y = 1
# plotting the graph
graph.triangle(x, y, size = 150)
# displaying the model
show(graph)
Output:
Refer to the below article to get detailed information about the triangles.
RectangleJust like circles and ovals rectangle can also be plotted in Bokeh. It can be plotted using the rect() method.
Syntax:
rect(parameters)
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title = "Bokeh Rectangle Graph", match_aspect = True)
# the points to be plotted
x = 0
y = 0
width = 10
height = 5
# plotting the graph
graph.rect(x, y, width, height)
# displaying the model
show(graph)
Output:
PolygonBokeh can also be used to plot multiple polygons on a graph. Plotting multiple polygons on a graph can be done using the multi_polygons() method of the plotting module.
Syntax:
multi_polygons(parameters)
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title = "Bokeh Multiple Polygons Graph")
# the points to be plotted
xs = [[[[1, 1, 3, 4]]]]
ys = [[[[1, 3, 2 ,1]]]]
# plotting the graph
graph.multi_polygons(xs, ys)
# displaying the model
show(graph)
Output:
Refer to the below articles to get detailed information about the polygon glyphs.
Plotting Multiple PlotsThere are several layouts provided by the Bokeh in order to create Multiple Plots. These layouts are:
Vertical Layout set all the plots in the vertical fashion and can be created using the column() method.
Python3
from bokeh.io import output_file, show
from bokeh.layouts import column
from bokeh.plotting import figure
x = [1, 2, 3, 4, 5, 6]
y0 = x
y1 = [i * 2 for i in x]
y2 = [i ** 2 for i in x]
# create a new plot
s1 = figure(width=200, plot_height=200)
s1.circle(x, y0, size=10, alpha=0.5)
# create another one
s2 = figure(width=200, height=200)
s2.triangle(x, y1, size=10, alpha=0.5)
# create and another
s3 = figure(width=200, height=200)
s3.square(x, y2, size=10, alpha=0.5)
# put all the plots in a VBox
p = column(s1, s2, s3)
# show the results
show(p)
Output:
Horizontal LayoutHorizontal Layout set all the plots in the horizontal fashion. It can be created using the row() method.
Example:
Python3
from bokeh.io import output_file, show
from bokeh.layouts import row
from bokeh.plotting import figure
x = [1, 2, 3, 4, 5, 6]
y0 = x
y1 = [i * 2 for i in x]
y2 = [i ** 2 for i in x]
# create a new plot
s1 = figure(width=200, plot_height=200)
s1.circle(x, y0, size=10, alpha=0.5)
# create another one
s2 = figure(width=200, height=200)
s2.triangle(x, y1, size=10, alpha=0.5)
# create and another
s3 = figure(width=200, height=200)
s3.square(x, y2, size=10, alpha=0.5)
# put all the plots in a VBox
p = row(s1, s2, s3)
# show the results
show(p)
Output:
Grid Layoutgridplot() method can be used to arrange all the plots in the grid fashion. we can also pass None to leave a space empty for a plot.
Example:
Python3
from bokeh.io import output_file, show
from bokeh.layouts import gridplot
from bokeh.plotting import figure
x = [1, 2, 3, 4, 5, 6]
y0 = x
y1 = [i * 2 for i in x]
y2 = [i ** 2 for i in x]
# create a new plot
s1 = figure()
s1.circle(x, y0, size=10, alpha=0.5)
# create another one
s2 = figure()
s2.triangle(x, y1, size=10, alpha=0.5)
# create and another
s3 = figure()
s3.square(x, y2, size=10, alpha=0.5)
# put all the plots in a grid
p = gridplot([[s1, None], [s2, s3]], plot_width=200, plot_height=200)
# show the results
show(p)
Output:
Interactive Data VisualizationOne of the key feature of Bokeh which differentiate it from other visualizing libraries is adding interaction to the Plot. Let's see various interactions that can be added to the plot.
Configuring Plot ToolsIn all the above graphs you must have noticed a toolbar that appears mostly at the right of the plot. Bokeh provides us the methods to handle these tools. Tools can be classified into four categories.
We can specify the position of the toolbar according to our own needs. It can be done by passing the toolbar_location parameter to the figure() method. The possible value to this parameter is -
Example:
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# instantiating the figure object
graph = figure(title = "Bokeh ToolBar", toolbar_location="below")
# the points to be plotted
x = [1, 2, 3, 4, 5]
y = [1, 2, 3, 4, 5]
# height / thickness of the plot
width = 0.5
# plotting the scatter graph
graph.scatter(x, y)
# displaying the model
show(graph)
Output:
Interactive LegendsIn the section annotations and legends we have seen the list of all the parameters of the legends, however, we have not discussed the click_policy parameter yet. This property makes the legend interactive. There are two types of interactivity -
Example 1: Hiding the legend
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# file to save the model
output_file("gfg.html")
# instantiating the figure object
graph = figure(title = "Bokeh Hiding Glyphs")
# plotting the graph
graph.vbar(x = 1, top = 5,
width = 1, color = "violet",
legend_label = "Violet Bar")
graph.vbar(x = 2, top = 5,
width = 1, color = "green",
legend_label = "Green Bar")
graph.vbar(x = 3, top = 5,
width = 1, color = "yellow",
legend_label = "Yellow Bar")
graph.vbar(x = 4, top = 5,
width = 1, color = "red",
legend_label = "Red Bar")
# enable hiding of the glyphs
graph.legend.click_policy = "hide"
# displaying the model
show(graph)
Output:
Example 2: Muting the legend
Python3
# importing the modules
from bokeh.plotting import figure, output_file, show
# file to save the model
output_file("gfg.html")
# instantiating the figure object
graph = figure(title = "Bokeh Hiding Glyphs")
# plotting the graph
graph.vbar(x = 1, top = 5,
width = 1, color = "violet",
legend_label = "Violet Bar",
muted_alpha=0.2)
graph.vbar(x = 2, top = 5,
width = 1, color = "green",
legend_label = "Green Bar",
muted_alpha=0.2)
graph.vbar(x = 3, top = 5,
width = 1, color = "yellow",
legend_label = "Yellow Bar",
muted_alpha=0.2)
graph.vbar(x = 4, top = 5,
width = 1, color = "red",
legend_label = "Red Bar",
muted_alpha=0.2)
# enable hiding of the glyphs
graph.legend.click_policy = "mute"
# displaying the model
show(graph)
Output:
Adding Widgets to the PlotBokeh provides GUI features similar to HTML forms like buttons, slider, checkbox, etc. These provide an interactive interface to the plot that allows to change the parameters of the plot, modifying plot data, etc. Let's see how to use and add some commonly used widgets.
Syntax:
Button(label, icon, callback)
Example:
Python3
from bokeh.io import show
from bokeh.models import Button, CustomJS
button = Button(label="GFG")
button.js_on_click(CustomJS(
code="console.log('button: click!', this.toString())"))
show(button)
Output:
Example:
Python3
from bokeh.io import show
from bokeh.models import CheckboxGroup, CustomJS
L = ["First", "Second", "Third"]
# the active parameter sets checks the selected value
# by default
checkbox_group = CheckboxGroup(labels=L, active=[0, 2])
checkbox_group.js_on_click(CustomJS(code="""
console.log('checkbox_group: active=' + this.active, this.toString())
"""))
show(checkbox_group)
Output:
Syntax:
RadioGroup(labels, active)
Example:
Python3
from bokeh.io import show
from bokeh.models import RadioGroup, CustomJS
L = ["First", "Second", "Third"]
# the active parameter sets checks the selected value
# by default
radio_group = RadioGroup(labels=L, active=1)
radio_group.js_on_click(CustomJS(code="""
console.log('radio_group: active=' + this.active, this.toString())
"""))
show(radio_group)
Output:
Syntax:
Slider(start, end, step, value)
Example:
Python3
from bokeh.io import show
from bokeh.models import CustomJS, Slider
slider = Slider(start=1, end=20, value=1, step=2, title="Slider")
slider.js_on_change("value", CustomJS(code="""
console.log('slider: value=' + this.value, this.toString())
"""))
show(slider)
Output:
Example:
Python3
from bokeh.io import show
from bokeh.models import CustomJS, Dropdown
menu = [("First", "First"), ("Second", "Second"), ("Third", "Third")]
dropdown = Dropdown(label="Dropdown Menu", button_type="success", menu=menu)
dropdown.js_on_event("menu_item_click", CustomJS(
code="console.log('dropdown: ' + this.item, this.toString())"))
show(dropdown)
Output:
Example:
Python3
from bokeh.plotting import figure, output_file, show
from bokeh.models import Panel, Tabs
import numpy as np
import math
fig1 = figure(plot_width=300, plot_height=300)
x = [1, 2, 3, 4, 5]
y = [5, 4, 3, 2, 1]
fig1.line(x, y, line_color='green')
tab1 = Panel(child=fig1, title="Tab 1")
fig2 = figure(plot_width=300, plot_height=300)
fig2.line(y, x, line_color='red')
tab2 = Panel(child=fig2, title="Tab 2")
all_tabs = Tabs(tabs=[tab1, tab2])
show(all_tabs)
Output:
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