5.1 Basic Plotting

Creating Figures

Note that Bokeh plots created using the bokeh.plotting interface comes with a default set of tools, and default visual styles. Later we will learn Styling Visual Attributes for information about how to customize the visual style of plots.

1. Scatter and Markers

All the markers have the same set of properties: x, y, size, and angle (radians by default).

# Standard import
from bokeh.plotting import figure, output_file, show
output_notebook()

# set the figure size and title
p = figure(plot_width=400, plot_height=400,title="Simple Scatter Plot")

# add a circle renderer with a size, color, and alpha
p.circle([2, 2, 3, 4, 5], [6, 7, 5, 4, 5], size=40, color="firebrick", alpha=0.7)
show(p)

Scatter Plots

There are lots of marker types available in Bokeh:

asterisk() circle() circle_cross() circle_dot() circle_x() circle_y() cross() dash() dot()	diamond() diamond_cross() diamond_dot() hex() hex_dot() inverted_triangle() plus() square() square_cross()	square_dot() square_pin() square_x() triangle() triangle_dot() triangle_pin() x()

2. Line Graphs

Single line and step line

Here is an example to generate a single line glyph from one-dimensional sequences of x and y points using the line() glyph method and how to draw discrete steps between data points with step() method.

from bokeh.layouts import row    #  create a multiple layouts

p1 = figure(plot_width=400, plot_height=400,title =  'Simple Line')
p1.line([1, 2, 3, 4, 5], [6, 7, 10, 9, 8], line_width=3,color =  'royalblue')

p2 = figure(plot_width=400, plot_height=400,title  = 'Step Line')
p2.step([1, 2, 3, 4, 5], [6, 7, 10, 9, 8], line_width=3,color =  'firebrick', mode='center')

show(row(p1,p2))  # show two figures in a row

Simple Line and Step Line

Multiple lines and stacked lines

Sometimes it is useful to plot multiple lines all at once. Then we can usemulti_line()to accomplish. In some instances, it is desirable to stack lines that are aligned on a common index (e.g. time series of percentages). Then we use vline_stack() or hline_stack().

from bokeh.models import ColumnDataSource   # create a simple dataset in Bokeh
source = ColumnDataSource(data=dict(
    x=[1, 2, 3, 4, 5],
    y1=[1, 2, 4, 3, 4],
    y2=[3, 4, 2, 5, 5],
))

p1 = figure(plot_width=400, plot_height=400, title ='Multiple Lines')

p1.multi_line([[2, 3, 4], [3, 4, 5, 6]], [[3, 4, 5], [6, 7, 8, 3]],
             color=["firebrick", "royalblue"], line_width=3)

p2 =  figure(plot_width=400, plot_height=400, title ='Stacked Lines')
p2.vline_stack(['y1', 'y2'], x='x',line_width  = 4, source=source)

show(row(p1,p2))

Multiple Lines and Stacked Lines

3. Bars

Vertical Bar and Horizontal Bar

When drawing rectangular bars (often representing intervals) it is often more convenient to have coordinates that are a hybrid of the two systems above.

• to draw vertical bars by specifying a (center) x-coordinate, width, and top and bottom endpoints, use the vbar() function.

• to draw horizontal bars by specifying a (center) y-coordinate, height, and left and right endpoints, use the hbar() function.

p1 = figure(plot_width=400, plot_height=400,title  ='Vertical Bar')
p1.vbar(x=[1, 2, 3], width=0.4, bottom=0,
       top=[2, 2.5, 3.8], color="salmon")

p2 = figure(plot_width=400, plot_height=400,title  ='Horizontal Bar')
p2.hbar(y=[1, 2, 3], height=0.4, left=0,
       right=[2, 2.5, 3.8], color="lightblue")
show(row(p1,p2))

Vertical Bar and Horizontal Bar

Stacked Bar

source = ColumnDataSource(data=dict(
    y=[1, 2, 3, 4, 5],
    x1=[1, 2, 4, 3, 4],
    x2=[1, 4, 2, 2, 3],
))

p = figure(plot_width=400, plot_height=400,title  = 'Stacked Bars')
p.hbar_stack(['x1', 'x2'], y='y', height=0.7, 
        color=("navy", "lightblue"), source=source)

show(p)

Stacked Bars

4. Directed Areas

Directed areas are filled regions between two series that share a common index. For instance, a vertical directed area has one x coordinate array, and two y coordinate arrays, y1 and y2, which will be filled between.

• A single directed area between two aligned series can be created in the vertical direction with varea() or in the horizontal direction with harea()

• The stacked area can be accomplished with the varea_stack() and harea_stack()

Single Area and Stacked Areas

source = ColumnDataSource(data=dict(
    x=[1, 2, 3, 4, 5],
    y1=[1, 2, 4, 3, 4],
    y2=[1, 4, 2, 2, 3],
))

p1 = figure(plot_width=400, plot_height=400,title ='Single Areas')
p1.varea(x='x',  y1='y1', y2='y2',source  = source, color = 'royalblue')

p2 = figure(plot_width=400, plot_height=400,title ='Stacked Areas')

p2.varea_stack(['y1', 'y2'], x='x', 
            color=("royalblue", "lightgrey"), source=source)

show(row(p1,p2))

Single Areas and Stacked Areas

5. Polygons

Below is an example that shows how to generate a single polygonal patch glyph from one- dimensional sequences of x and y points using the patch() method and how to plot multiple polygonal patches all at once using patches()

p1 = figure(plot_width=400, plot_height=400, title = 'Single Patch')

# add a patch renderer with an alpha an line width
p1.patch([1, 2, 3, 4,5], [3,2,3,4,3], color = 'salmon',  alpha=0.8, line_width=2)

p2 = figure(plot_width=400, plot_height=400,title  = 'Multiple Patches')

p2.patches([[1, 3, 2], [3, 4, 6, 6]], [[2, 1, 4], [4, 7, 8, 5]],
          color=["Salmon", "cyan"], alpha=[0.8, 0.5])


show(row(p1,p2))

Single Patch and Multiple Patches

6. Wedges and Arcs

p1 = figure(plot_width=400, plot_height=400,title  = 'Annular Wedge')
p1.annular_wedge(x=[1, 2, 3], y=[2, 2, 2], inner_radius=0.1, outer_radius=0.25,
                start_angle=0.4, end_angle=4.8, color="cyan", alpha=0.7)

p2 = figure(plot_width=400, plot_height=400,title = 'Annulus')
p2.annulus(x=[1, 2, 3], y=[3, 2, 1], inner_radius=0.1, outer_radius=0.25,
          color="orange", alpha=0.8)

show(row(p1,p2))

Wedges and Arcs

7. Combining Glyphs and Setting Range

• Combining multiple glyphs on a single plot is a matter of calling more than one glyph method on a single Figure

• By default, Bokeh will attempt to automatically set the data bounds of plots to fit snugly around the data. Sometimes, you may need to set a plot’s range explicitly. Then we use x_range and y_range

x = [1, 2, 3, 4, 5]
y = [3, 6, 4, 7,6 ]

p1 = figure(plot_width=400, plot_height=400,title  = 'Line + Scatter')
# add both a line and circles on the same plot
p1.line(x, y, line_width=3,color = 'orange')
p1.circle(x, y, fill_color="white", size=12)

p2 = figure(plot_width=400, plot_height=400, x_range=(0,5), y_range = (0,7),title = 'Setting Ranges')
p2.line(x, y, line_width=3,color = 'orange')
show(row(p1,p2))

Combining Glyphs and Setting Range

As we can see from the graph, the left one combines the line chart and circle chart to show the trends. Also, the X-axis and Y-axis of the left one do not start with 0. We set the range in the right one and make sure the graph has not been misinterpreted.