Skip to content

add docstring for ax.quiver, including a return section #19562

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 1 commit into from
Closed
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
167 changes: 167 additions & 0 deletions lib/matplotlib/axes/_axes.py
Original file line number Diff line number Diff line change
Expand Up @@ -5089,6 +5089,173 @@ def _quiver_units(self, args, kw):
# args can by a combination if X, Y, U, V, C and all should be replaced
@_preprocess_data()
def quiver(self, *args, **kw):
"""
Plot a 2D field of arrows.

Call signature::

quiver([X, Y], U, V, [C], **kw)

*X*, *Y* define the arrow locations, *U*, *V* define the arrow directions, and
*C* optionally sets the color.

**Arrow size**

The default settings auto-scales the length of the arrows to a reasonable size.
To change this behavior see the *scale* and *scale_units* parameters.

**Arrow shape**

The defaults give a slightly swept-back arrow; to make the head a
triangle, make *headaxislength* the same as *headlength*. To make the
arrow more pointed, reduce *headwidth* or increase *headlength* and
*headaxislength*. To make the head smaller relative to the shaft,
scale down all the head parameters. You will probably do best to leave
minshaft alone.

**Arrow outline**

*linewidths* and *edgecolors* can be used to customize the arrow
outlines.

Parameters
----------
X, Y : 1D or 2D array-like, optional
The x and y coordinates of the arrow locations.

If not given, they will be generated as a uniform integer meshgrid based
on the dimensions of *U* and *V*.

If *X* and *Y* are 1D but *U*, *V* are 2D, *X*, *Y* are expanded to 2D
using ``X, Y = np.meshgrid(X, Y)``. In this case ``len(X)`` and ``len(Y)``
must match the column and row dimensions of *U* and *V*.

U, V : 1D or 2D array-like
The x and y direction components of the arrow vectors.

They must have the same number of elements, matching the number of arrow
locations. *U* and *V* may be masked. Only locations unmasked in
*U*, *V*, and *C* will be drawn.

C : 1D or 2D array-like, optional
Numeric data that defines the arrow colors by colormapping via *norm* and
*cmap*.

This does not support explicit colors. If you want to set colors directly,
use *color* instead. The size of *C* must match the number of arrow
locations.

units : {'width', 'height', 'dots', 'inches', 'x', 'y', 'xy'}, default: 'width'
The arrow dimensions (except for *length*) are measured in multiples of
this unit.

The following values are supported:

- 'width', 'height': The width or height of the axis.
- 'dots', 'inches': Pixels or inches based on the figure dpi.
- 'x', 'y', 'xy': *X*, *Y* or :math:`\\sqrt{X^2 + Y^2}` in data units.

The arrows scale differently depending on the units. For
'x' or 'y', the arrows get larger as one zooms in; for other
units, the arrow size is independent of the zoom state. For
'width or 'height', the arrow size increases with the width and
height of the axes, respectively, when the window is resized;
for 'dots' or 'inches', resizing does not change the arrows.

angles : {'uv', 'xy'} or array-like, default: 'uv'
Method for determining the angle of the arrows.

- 'uv': The arrow axis aspect ratio is 1 so that
if *U* == *V* the orientation of the arrow on the plot is 45 degrees
counter-clockwise from the horizontal axis (positive to the right).

Use this if the arrows symbolize a quantity that is not based on
*X*, *Y* data coordinates.

- 'xy': Arrows point from (x, y) to (x+u, y+v).
Use this for plotting a gradient field, for example.

- Alternatively, arbitrary angles may be specified explicitly as an array
of values in degrees, counter-clockwise from the horizontal axis.

In this case *U*, *V* is only used to determine the length of the
arrows.

Note: inverting a data axis will correspondingly invert the
arrows only with ``angles='xy'``.

scale : float, optional
Number of data units per arrow length unit, e.g., m/s per plot width; a
smaller scale parameter makes the arrow longer. Default is *None*.

If *None*, a simple autoscaling algorithm is used, based on the average
vector length and the number of vectors. The arrow length unit is given by
the *scale_units* parameter.

scale_units : {'width', 'height', 'dots', 'inches', 'x', 'y', 'xy'}, optional
If the *scale* kwarg is *None*, the arrow length unit. Default is *None*.

e.g. *scale_units* is 'inches', *scale* is 2.0, and ``(u, v) = (1, 0)``,
then the vector will be 0.5 inches long.

If *scale_units* is 'width' or 'height', then the vector will be half the
width/height of the axes.

If *scale_units* is 'x' then the vector will be 0.5 x-axis
units. To plot vectors in the x-y plane, with u and v having
the same units as x and y, use
``angles='xy', scale_units='xy', scale=1``.

width : float, optional
Shaft width in arrow units; default depends on choice of units,
above, and number of vectors; a typical starting value is about
0.005 times the width of the plot.

headwidth : float, default: 3
Head width as multiple of shaft width.

headlength : float, default: 5
Head length as multiple of shaft width.

headaxislength : float, default: 4.5
Head length at shaft intersection.

minshaft : float, default: 1
Length below which arrow scales, in units of head length. Do not
set this to less than 1, or small arrows will look terrible!

minlength : float, default: 1
Minimum length as a multiple of shaft width; if an arrow length
is less than this, plot a dot (hexagon) of this diameter instead.

pivot : {'tail', 'mid', 'middle', 'tip'}, default: 'tail'
The part of the arrow that is anchored to the *X*, *Y* grid. The arrow
rotates about this point.

'mid' is a synonym for 'middle'.

color : color or color sequence, optional
Explicit color(s) for the arrows. If *C* has been set, *color* has no
effect.

This is a synonym for the `~.PolyCollection` *facecolor* parameter.

Other Parameters
----------------
**kwargs : `~matplotlib.collections.PolyCollection` properties, optional
All other keyword arguments are passed on to `.PolyCollection`:

%(PolyCollection_kwdoc)s

Returns
----------------
The new `matplotlib.quiver.Quiver` object.


See Also
--------
.Axes.quiverkey : Add a key to a quiver plot.
""" % docstring.interpd.params
# Make sure units are handled for x and y values
args = self._quiver_units(args, kw)

Expand Down