foxplot 0.6.0

Plot time-series data from line-delimited JSON.

foxplot

Plot time series from newline-delimited JSON.

Installation

pip install foxplot

Usage

Foxplot starts in interactive mode by default to explore the input gathered in data (tab completion works: try data.<TAB>). Plot times series using the fox.plot function, for example:

$ foxplot upkie_2023-05-03-103245.mpack
Python 3.8.10 (default, Mar 13 2023, 10:26:41)
Type 'copyright', 'credits' or 'license' for more information
IPython 8.0.1 -- An enhanced Interactive Python. Type '?' for help.

In [1]: fox.plot(data.observation.imu.angular_velocity)

This call opens a new tab in your browser with the desired plot. In this example, angular_velocity is a 3D vector, thus the plot will include three curves.

Left and right axes

Here is a plot with both left- and right-axis time series:

In [2]: fox.plot(
   ...:     [
   ...:         data.observation.servo.left_knee.position,
   ...:         data.observation.servo.left_wheel.position,
   ...:     ],
   ...:     right=[
   ...:         data.observation.servo.left_knee.velocity,
   ...:         data.observation.servo.left_wheel.velocity,
   ...:     ],
   ...:     left_axis_unit="rad",
   ...:     right_axis_unit="rad/s",
   ...:     print_command_line=True,
   ...: )

Check out the other arguments to fox.plot in its documentation (IPython: fox.plot?).

Computing new series

Time series are labeled NumPy arrays, and can be manipulated as such. For example:

In [1]: left_knee = data.observation.servo.left_knee

In [2]: left_knee_power = left_knee.torque * left_knee.velocity

In [3]: fox.plot(left_knee_power, right=[left_knee.velocity])

Plotting from files

We can also plot data from files and pipes directly, for example:

• JSON: foxplot my_data.json -l /observation/cpu_temperature
• MessagePack: foxplot my_data.mpack -l /observation/cpu_temperature

Tips

Zsh users can filter foxplot completion on JSON and MessagePack files:

zstyle ":completion:*:*:foxplot:*" ignored-patterns "^*.(json|mpack)"

See also

• µPlot: time-series plotting library, whose performance was a key enabler for this project.

• mpacklog.cpp: library to log dictionaries to MessagePack files in C++.
• mpacklog.py: library and command-line tools to log dictionaries to MessagePack files in Python.

• rq: command-line tool to manipulate streams of records in various formats.