Matplotlib.patches.Arrow Class in Python

Matplotlib is an amazing visualization library in Python for 2D plots of arrays. Matplotlib is a multi-platform data visualization library built on NumPy arrays and designed to work with the broader SciPy stack.

Matplotlib.patches.Arrow

The matplotlib.patches.Arrow class is used to for patching an arrow in the plot. it draws arrow from (x, y) to (x + dx, y + dy) and its width is scaled using the width argument.

Syntax: class matplotlib.patches.Arrow(x, y, dx, dy, width=1.0, **kwargs)

Parameters:

1. x: It represents the x coordinate of the arrow tail.
2. y: It represents the y coordinate of the arrow tail.
3. dx: It represents arrow length in the x direction.
4. dy: It represents arrow length in the y direction.
5. width: It is an optional parameter and has default value as 1. it is the scale factor for the width of the arrow. In default value the tail width is 0.2 and the head width is 0.6.
6. **kwargs: These are the patch properties mentioned below in the table;

Property	Description
agg_filter	a filter function that takes a (m, n, 3) float array and a dpi value that returns a (m, n, 3) array
alpha	float or None
animated	bool
antialiased or aa	unknown
capstyle	{‘butt’, ’round’, ‘projecting’}
clip_box	Bbox
clip_on	bool
clip_path	[(Path, Transform)|Patch|None]
color	color or sequence of rgba tuples
contains	callable
edgecolor or ec or edgecolors	color or None or ‘auto’
facecolor or fc or facecolors	color or None
figure	figure
fill	bool
gid	str
hatch	{‘/’, ‘\’, ‘|’, ‘-‘, ‘+’, ‘x’, ‘o’, ‘O’, ‘.’, ‘*’}
in_layout	bool
joinstyle	{‘miter’, ’round’, ‘bevel’}
linestyle or ls	{‘-‘, ‘–‘, ‘-.’, ‘:’, ”, (offset, on-off-seq), …}
linewidth or linewidths or lw	float or None
path_effects	AbstractPathEffect
picker	None or bool or float or callable
path_effects	AbstractPathEffect
picker	float or callable[[Artist, Event], Tuple[bool, dict]]
rasterized	bool or None
sketch_params	(scale: float, length: float, randomness: float)
snap	bool or None
transform	matplotlib.transforms.Transform
url	str
visible	bool
zorder	float

Example 1:

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.path as mpath
import matplotlib.lines as mlines
import matplotlib.patches as mpatches
from matplotlib.collections import PatchCollection


def label(xy, text):

    # shift y-value for label so that
    # it's below the artist
    y = xy[1] - 0.15
    plt.text(xy[0], y, text, ha ="center",
             family ='sans-serif', size = 14)


fig, ax = plt.subplots()

# create 3x3 grid to plot
# the artists
grid = np.mgrid[0.2:0.8:3j,
                0.2:0.8:3j].reshape(2, -1).T

patches = []


# add an arrow
arrow = mpatches.Arrow(grid[5, 0] - 0.05,
                       grid[5, 1] - 0.05, 0.1, 0.1,
                       width = 0.1)
patches.append(arrow)
label(grid[5], " Sample Arrow")


colors = np.linspace(0, 1, len(patches))
collection = PatchCollection(patches,
                             cmap = plt.cm.hsv,
                             alpha = 0.3)

collection.set_array(np.array(colors))
ax.add_collection(collection)

plt.axis('equal')
plt.axis('off')
plt.tight_layout()

plt.show()

Output:

Example 2:

from matplotlib import pyplot as plt
from matplotlib.patches import Rectangle, Arrow
import numpy as np


nmax = 9
xdata = range(nmax)
ydata = np.random.random(nmax)

plt.ion()
fig, ax = plt.subplots()
ax.set_aspect("equal")
ax.plot(xdata, ydata, 'o-')
ax.set_xlim(-1, 10)
ax.set_ylim(-1, 4)


rect = Rectangle((0, 0), nmax, 1, zorder = 10)
ax.add_patch(rect)

x0, y0 = 5, 3
arrow = Arrow(1, 1, x0-1, y0-1, color ="# aa0088")

a = ax.add_patch(arrow)

plt.draw()

for i in range(nmax):

    rect.set_x(i)
    rect.set_width(nmax - i)

    a.remove()
    arrow = Arrow(1 + i, 1, x0-i + 1, y0-1,
                  color ="# aa0088")
    a = ax.add_patch(arrow)

    fig.canvas.draw_idle()
    plt.pause(0.4)

plt.waitforbuttonpress()

plt.show()

Output: