drawarrow 0.0.2

Drawing arrows for matplotlib made easy.

drawarrow

Drawing arrows for matplotlib made easy.

Table of content:

• Installation
• Quick Start
• Usage guide
• Contributing

Installation

You can install drawarrow directly from PyPI with:

pip install drawarrow

Alternatively you can install the development version with:

pip install git+https://github.com/JosephBARBIERDARNAL/drawarrow.git

Quick Start

import matplotlib.pyplot as plt
from drawarrow import fig_arrow

fig, ax = plt.subplots()

ax.scatter(x=[1, 2, 3, 4, 5], y=[1, 2, 3, 4, 5], s=100)

fig_arrow(head_position=(0.5, 0.5), tail_position=(0.2, 0.7), fig=fig, color="r")

plt.show()

Usage guide

drawarrow provides 2 functions:

• fig_arrow(): draw an arrow on a Matplotlib figure (e.g. the whole chart)
• ax_arrow(): draw an arrow on Matplotlib axes (e.g. a subplot)

The difference between those functions mainly lies in their coordinates. An arrow on a Figure would usually be between 0 and 1 for both x and y axis. However, when drawing an arrow on an Axes, it's on the data coordinates.

Those functions have a set a common arguments:

• tail_position (array-like of length 2): position of the tail of the arrow (on the figure/axes)
• head_position (array-like of length 2): position of the head of the arrow (on the figure/axes)
• invert (bool, default to False): whether to invert or not the angle of the arrow (only used if radius!=0)
• radius (float, default to 0.1):
• tail_width (float, default to 0.5): Width of the tail of the arrow
• head_width (float, default to 4): Head width of the tail of the arrow
• head_length (float, default to 8): Head length of the tail of the arrow
• linewidth (float, default to 0.5): Width of the body of the arrow
• color: color of the arrow,

ax_arrow()

This function is recommended when what you want to highlight is related to the data itself, such as a specific point in a scatter plot.

Minimalist usage

import matplotlib.pyplot as plt
from drawarrow import ax_arrow

fig, ax = plt.subplots()
ax.scatter(x=[1, 5, 10], y=[5, 12, 3])
ax_arrow((2, 8), (8, 2), ax=ax, color="blue", radius=0.3)
plt.show()

Usage with multiple subplots

import matplotlib.pyplot as plt
from drawarrow import ax_arrow

fig, axs = plt.subplots(ncols=3, nrows=3)

for ax in axs.flat:
    ax.set_xlim(0, 10)
    ax.set_ylim(0, 10)
    ax.set_xticks([])
    ax.set_yticks([])

    ax_arrow((2, 2), (8, 8), ax=ax, color="red", radius=0.4)
plt.show()

fig_arrow()

Minimalist usage

This function is recommended when what you want to highlight something that is more global and not data specific.

import matplotlib.pyplot as plt
from drawarrow import fig_arrow

fig, ax = plt.subplots()
fig_arrow((0.3, 0.3), (0.8, 0.8), fig=fig)

plt.show()

More complex usage

import matplotlib.pyplot as plt
from drawarrow import fig_arrow

fig, ax = plt.subplots()
fig_arrow(
    (0.3, 0.3),
    (0.8, 0.8),
    color="#2a9d8f",
    tail_width=2,
    head_length=20,
    head_width=10,
    linewidth=2,
    radius=0.7,
    invert=True,
    fig=fig,
)

plt.show()

Tips and tricks

Straight arrow

To draw a straight arrow, you just have to pass radius=0:

import matplotlib.pyplot as plt
from drawarrow import fig_arrow

fig, ax = plt.subplots()
fig_arrow((0.3, 0.3), (0.8, 0.8), radius=0, fig=fig)

plt.show()

Back and forth arrow

radius has no real bounds in terms of possible values:

import matplotlib.pyplot as plt
from drawarrow import fig_arrow

fig, ax = plt.subplots()
fig_arrow((0.3, 0.3), (0.8, 0.8), radius=2, fig=fig)

plt.show()

Contributions

Contributions (and feedback) are welcome.

TODO features:

• control opacity (alpha parameter in matplotlib)
• control zorder
• draw arrow with an inflection point (see this)
• ...

Installation for contributions

Note: the following steps are for Mac, but not very different in other OS.

• Fork this repo
• git clone https://github.com/yourusername/drawarrow.git
• cd drawarrow
• python -m venv venv
• source venv/bin/activate
• pip install -r requirements.txt
• pip install -e .
• git checkout -b feature-name
• start coding!

Acknowledgement

Thanks pizzadude for the font used in the logo.