.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "gallery/shapes_and_collections/arrow_guide.py" .. LINE NUMBERS ARE GIVEN BELOW. .. only:: html .. meta:: :keywords: codex .. note:: :class: sphx-glr-download-link-note :ref:`Go to the end ` to download the full example code .. rst-class:: sphx-glr-example-title .. _sphx_glr_gallery_shapes_and_collections_arrow_guide.py: =========== Arrow guide =========== Adding arrow patches to plots. Arrows are often used to annotate plots. This tutorial shows how to plot arrows that behave differently when the data limits on a plot are changed. In general, points on a plot can either be fixed in "data space" or "display space". Something plotted in data space moves when the data limits are altered - an example would be the points in a scatter plot. Something plotted in display space stays static when data limits are altered - an example would be a figure title or the axis labels. Arrows consist of a head (and possibly a tail) and a stem drawn between a start point and end point, called 'anchor points' from now on. Here we show three use cases for plotting arrows, depending on whether the head or anchor points need to be fixed in data or display space: 1. Head shape fixed in display space, anchor points fixed in data space 2. Head shape and anchor points fixed in display space 3. Entire patch fixed in data space Below each use case is presented in turn. .. redirect-from:: /gallery/text_labels_and_annotations/arrow_simple_demo .. GENERATED FROM PYTHON SOURCE LINES 29-42 .. code-block:: Python import matplotlib.pyplot as plt import matplotlib.patches as mpatches x_tail = 0.1 y_tail = 0.5 x_head = 0.9 y_head = 0.8 dx = x_head - x_tail dy = y_head - y_tail .. GENERATED FROM PYTHON SOURCE LINES 43-53 Head shape fixed in display space and anchor points fixed in data space ----------------------------------------------------------------------- This is useful if you are annotating a plot, and don't want the arrow to change shape or position if you pan or scale the plot. In this case we use `.patches.FancyArrowPatch`. Note that when the axis limits are changed, the arrow shape stays the same, but the anchor points move. .. GENERATED FROM PYTHON SOURCE LINES 53-64 .. code-block:: Python fig, axs = plt.subplots(nrows=2) arrow = mpatches.FancyArrowPatch((x_tail, y_tail), (x_head, y_head), mutation_scale=100) axs[0].add_patch(arrow) arrow = mpatches.FancyArrowPatch((x_tail, y_tail), (x_head, y_head), mutation_scale=100) axs[1].add_patch(arrow) axs[1].set(xlim=(0, 2), ylim=(0, 2)) .. image-sg:: /gallery/shapes_and_collections/images/sphx_glr_arrow_guide_001.png :alt: arrow guide :srcset: /gallery/shapes_and_collections/images/sphx_glr_arrow_guide_001.png, /gallery/shapes_and_collections/images/sphx_glr_arrow_guide_001_2_00x.png 2.00x :class: sphx-glr-single-img .. GENERATED FROM PYTHON SOURCE LINES 65-77 Head shape and anchor points fixed in display space --------------------------------------------------- This is useful if you are annotating a plot, and don't want the arrow to change shape or position if you pan or scale the plot. In this case we use `.patches.FancyArrowPatch`, and pass the keyword argument ``transform=ax.transAxes`` where ``ax`` is the axes we are adding the patch to. Note that when the axis limits are changed, the arrow shape and location stay the same. .. GENERATED FROM PYTHON SOURCE LINES 77-91 .. code-block:: Python fig, axs = plt.subplots(nrows=2) arrow = mpatches.FancyArrowPatch((x_tail, y_tail), (x_head, y_head), mutation_scale=100, transform=axs[0].transAxes) axs[0].add_patch(arrow) arrow = mpatches.FancyArrowPatch((x_tail, y_tail), (x_head, y_head), mutation_scale=100, transform=axs[1].transAxes) axs[1].add_patch(arrow) axs[1].set(xlim=(0, 2), ylim=(0, 2)) .. image-sg:: /gallery/shapes_and_collections/images/sphx_glr_arrow_guide_002.png :alt: arrow guide :srcset: /gallery/shapes_and_collections/images/sphx_glr_arrow_guide_002.png, /gallery/shapes_and_collections/images/sphx_glr_arrow_guide_002_2_00x.png 2.00x :class: sphx-glr-single-img .. GENERATED FROM PYTHON SOURCE LINES 92-105 Head shape and anchor points fixed in data space ------------------------------------------------ In this case we use `.patches.Arrow`, or `.patches.FancyArrow` (the latter is in orange). Note that when the axis limits are changed, the arrow shape and location change. `.FancyArrow`'s API is relatively awkward, and requires in particular passing ``length_includes_head=True`` so that the arrow *tip* is ``(dx, dy)`` away from the arrow start. It is only included in this reference because it is the arrow class returned by `.Axes.arrow` (in green). .. GENERATED FROM PYTHON SOURCE LINES 105-125 .. code-block:: Python fig, axs = plt.subplots(nrows=2) arrow = mpatches.Arrow(x_tail, y_tail, dx, dy) axs[0].add_patch(arrow) arrow = mpatches.FancyArrow(x_tail, y_tail - .4, dx, dy, width=.1, length_includes_head=True, color="C1") axs[0].add_patch(arrow) axs[0].arrow(x_tail + 1, y_tail - .4, dx, dy, width=.1, length_includes_head=True, color="C2") arrow = mpatches.Arrow(x_tail, y_tail, dx, dy) axs[1].add_patch(arrow) arrow = mpatches.FancyArrow(x_tail, y_tail - .4, dx, dy, width=.1, length_includes_head=True, color="C1") axs[1].add_patch(arrow) axs[1].arrow(x_tail + 1, y_tail - .4, dx, dy, width=.1, length_includes_head=True, color="C2") axs[1].set(xlim=(0, 2), ylim=(0, 2)) .. image-sg:: /gallery/shapes_and_collections/images/sphx_glr_arrow_guide_003.png :alt: arrow guide :srcset: /gallery/shapes_and_collections/images/sphx_glr_arrow_guide_003.png, /gallery/shapes_and_collections/images/sphx_glr_arrow_guide_003_2_00x.png 2.00x :class: sphx-glr-single-img .. GENERATED FROM PYTHON SOURCE LINES 126-128 .. code-block:: Python plt.show() .. rst-class:: sphx-glr-timing **Total running time of the script:** (0 minutes 1.181 seconds) .. _sphx_glr_download_gallery_shapes_and_collections_arrow_guide.py: .. only:: html .. container:: sphx-glr-footer sphx-glr-footer-example .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: arrow_guide.ipynb ` .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: arrow_guide.py ` .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_