swarm

Swarm plots show the distribution of values in a numerical column optionally grouped by categorical columns.

Usage

gurita swarm [-h] [-x COLUMN] [-y COLUMN] ... other arguments ...

Arguments

Argument	Description	Reference
-h	display help	help
-x COLUMN --xaxis COLUMN	select column for the X axis	X axis
-y COLUMN --yaxis COLUMN	select column for the Y axis	Y axis
--orient {v,h}	Orientation of plot. Allowed values: v = vertical, h = horizontal. Default: v.	orient
--order VALUE [VALUE ...]	controlling the order of the plotted swarms	order
--hue COLUMN	colour and/or group columns by hue	hue
--dodge	separate hue levels along the categorical axis	dodge
--hueorder VALUE [VALUE ...]	order of hue columns	hue order
--logx	log scale X axis	log X
--logy	log scale Y axis	log Y
--xlim BOUND BOUND	range limit X axis	limit X axis
--ylim BOUND BOUND	range limit Y axis	limit Y axis
--frow COLUMN	column to use for facet rows	facet rows
--fcol COLUMN	column to use for facet columns	facet columns
--fcolwrap INT	wrap the facet column at this width, to span multiple rows	facet wrap

See also

Similar functionality to swarm plots are provided by:

• Box plots

• Violin plots

• Strip plots

• Boxen plots

Swarm plots are based on Seaborn’s catplot library function, using the kind="swarm" option.

Warning

Swarm plots can be slow to render on input data sets with large numbers of rows. In cases where the swarm plot is too slow to render, consider using an alternative distribution plot, such as strip, box, boxen, or violin. Alternatively you can reduce the number of rows using a random sample of the data.

Simple example

Swarm plot of the age numerical column from the titanic.csv input file:

gurita swarm -y age < titanic.csv

The output of the above command is written to swarm.age.png:

The plotted numerical column can be divided into groups based on a categorical column. In the following example the distribution of age is shown for each value in the class column:

gurita swarm -y age -x class < titanic.csv

The output of the above command is written to swarm.class.age.png:

Getting help

The full set of command line arguments for swarm plots can be obtained with the -h or --help arguments:

gurita swarm -h

Selecting columns to plot

-x COLUMN, --xaxis COLUMN
-y COLUMN, --yaxis COLUMN

Swarm plots can be plotted for numerical columns and optionally grouped by categorical columns.

If no categorical column is specified, a single column swarm plot will be generated showing the distribution of the numerical column.

Note

By default the orientation of the swarm plot is vertical. In this scenario the numerical column is specified by -y, and the (optional) categorical column is specified by -x.

However, the orientation of the swarm plot can be made horizontal using the --orient h argument. In this case the sense of the X and Y axes are swapped from the default, and thus the numerical column is specified by -x, and the (optional) categorical column is specified by -y.

In the following example the distribution of age is shown for each value in the class column, where the boxes are plotted horizontally:

gurita swarm -x age -y class --orient h < titanic.csv

Controlling the order of the swarms

--order VALUE [VALUE ...]

By default the order of the categorical columns displayed in the swarm plot is determined from their occurrence in the input data. This can be overridden with the --order argument, which allows you to specify the exact ordering of columns based on their values.

In the following example the swarm columns of the class column are displayed in the order of First, Second, Third:

gurita swarm -y age -x class --order First Second Third < titanic.csv

Colour and/or group columns with hue

--hue COLUMN

Each swrm can be coloured and optionally subdivided into additional categories with the --hue argument.

The following example generates a swarm plot showing the distribution of the age of titanic passengers across the three different ticket classes, where each class is coloured differently:

gurita swarm -y age -x class --hue class < titanic.csv

In the following example the distribution of age is shown for each value in the class column, and further sub-divided by the sex column:

gurita swarm -y age -x class --hue sex < titanic.csv

As the previous example demonstrates, when --hue is used, by default all hue levels are shown mixed together in the same swarm. However, you might want to show each hue level in its own swarm. This can be achieved with the --dodge command.

The --dodge argument will separate hue levels along the categorical axis, rather than mix them together:

gurita swarm -y age -x class --hue sex --dodge < titanic.csv

By default the order of the columns within each hue group is determined from their occurrence in the input data. This can be overridden with the --hueorder argument, which allows you to specify the exact ordering of columns within each hue group, based on their values.

In the following example the sex values are displayed in the order of female, male:

gurita swarm -y age -x class --hue sex --hueorder female male < titanic.csv

It is also possible to use both --order and --hueorder in the same command. For example, the following command controls the order of both the class and sex categorical columns:

gurita swarm -y age -x class --order First Second Third --hue sex --hueorder female male < titanic.csv

Log scale

--logx
--logy

The distribution of numerical values can be displayed in log (base 10) scale with --logx and --logy.

It only makes sense to log-scale the numerical axis (and not the categorical axis). Therefore, --logx should be used when numerical columns are selected with -x, and conversely, --logy should be used when numerical columns are selected with -y.

For example, you can display a log scale swarm plot for the age column grouped by class (when the distribution of age is displayed on the Y axis) like so. Note carefully that the numerical data is displayed on the Y-axis (-y), therefore the --logy argument should be used to log-scale the numerical distribution:

gurita swarm -y age -x class --logy < titanic.csv

Axis range limits

--xlim LOW HIGH
--ylim LOW HIGH

The range of displayed numerical distributions can be restricted with --xlim and --ylim. Each of these flags takes two numerical values as arguments that represent the lower and upper bounds of the range to be displayed.

It only makes sense to range-limit the numerical axis (and not the categorical axis). Therefore, --xlim should be used when numerical columns are selected with -x, and conversely, --ylim should be used when numerical columns are selected with -y.

For example, you can display range-limited range for the age column grouped by class (when the distribution of age is displayed on the Y axis) like so. Note carefully that the numerical data is displayed on the Y-axis (-y), therefore the --ylim argument should be used to range-limit the distribution:

gurita swarm -y age -x class --ylim 10 30 < titanic.csv

Facets

--frow COLUMN
--fcol COLUMN
--fcolwrap INT

Swarm plots can be further divided into facets, generating a matrix of swarm plots, where a numerical value is further categorised by up to 2 more categorical columns.

See the facet documentation for more information on this feature.

The follow command creates a faceted swarm plot where the sex column is used to determine the facet columns:

gurita swarm -y age -x class --fcol sex < titanic.csv