Added arrowhead positioning options to quiver. #15396

PipGrylls · 2019-10-09T08:07:13Z

PR Summary

the optional keywords 'head_pos' has been added to quiver. 'head_pos' can put the arrowhead at the tip tail or middle of the arrow shaft dictated by keywords matching 'pivot', or be passed a float in range 0-1 to specify the exact location on the arrow shaft.

PR Checklist

Has Pytest style unit tests
Code is Flake 8 compliant
New features are documented, with examples if plot related
Documentation is sphinx and numpydoc compliant
Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way

anntzer · 2019-10-09T08:29:35Z

lib/matplotlib/quiver.py

@@ -173,6 +174,15 @@

    'mid' is a synonym for 'middle'.

+head_pos : {'tail', 'mid', 'middle', 'tip'}, optional, default: 'tip'


I would suggest having a single head_pos argument that takes either a string or a float, with "tail" synonymous to 0, "middle" synonymous to 0.5, and tip synonymous to 1 (or reverse 0 and 1 -- it's actually not clear from the docstring which is which).
Also perhaps the pivot kwarg should also gain the same functionality?

I was following the style of pivot for similarity within the module. But in principle, I agree with you both should probably be more flexible. I am not sure however if the angles become significantly more complex if the pivot parameter is let loose.

I have made the edits to head_pos and committed changes I have not edited pivot but this could be opened as a feature request should people actually want it.

anntzer · 2019-10-09T08:31:10Z

lib/matplotlib/quiver.py

+        if 0.0 < mid_scale < 1.0:
+            self.mid_scale = mid_scale
+        else:
+            self.mid_scale = 0.5


please error out in that case ("Errors should never pass silently.")
... or perhaps it actually makes sense to allow arrowheads outside of the shaft?

I was thinking about this perhaps they should be left to be as the user specified and throw instead a warning that the arrows will be off the shaft?
If I have more time I would also think about allowing this to be a 1D array to allow the arrowhead position on the shaft to convey extra information. This would be a reason for mid_scale and head_pos to stay independent I think as your other comment.

For now, I would just error out. We can always expand the functionality later on if there is demand.

I have made the edits and committed changes

timhoffm · 2019-10-14T11:26:22Z

Please add E402 for quiver_head_pos_demo.py in .flake8.

examples/images_contours_and_fields/quiver_head_pos_demo.py

QuLogic · 2020-09-25T06:54:43Z

The idea of this looks sound, and it doesn't appear that there's any opposition, but it seems to have been forgotten for a while. It now needs a rebase to fix conflicts, and there may be a few small typos to fix.

…n error outside the range thow a value error instead of defaulting to 0.5

examples/images_contours_and_fields/quiver_head_pos_demo.py

lib/matplotlib/quiver.py

QuLogic · 2020-09-25T21:14:06Z

lib/matplotlib/quiver.py

-        self._axes = ax  # The attr actually set by the Artist.axes property.
+        self.ax = ax
+        # modified quiver to allow for positioning of the arrowheads on the
+        # shaft


I don't think this change is intentional

QuLogic · 2020-09-25T21:16:46Z

lib/matplotlib/quiver.py

@@ -487,6 +498,25 @@ def __init__(self, ax, *args,
        self.angles = angles
        self.width = width

+        # Checks the boundaries of mid_scale if outside range default of 0.5
+        if (head_pos == 0.0) or (head_pos == "tail"):


There's no need to check both 0.0 and 'tail'. Instead, check for 'tail' (and the other strings), and set head_pos = 0.0 as appropriate. Then do a final check for 0.0 <= head_pos <= 1.0.

QuLogic · 2020-09-25T21:18:33Z

lib/matplotlib/quiver.py

@@ -50,7 +50,8 @@
 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.
+minshaft alone. To set the position of the arrowhead used *head_pos* and
+to exactly position the head on the shaft use *mid_scale*.


What is mid_scale? It doesn't appear to be part of this PR.

QuLogic · 2020-09-25T21:19:21Z

lib/matplotlib/quiver.py

+            Y[:, 6] = np.ones(np.shape(Y[:, 6])) * 0.5
+            Y[:, 5:-1] *= -1
+        else:
+            raise ValueError("'head_pos' must be "


This has already been checked earlier, so no need to do so again.

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

dopplershift · 2020-09-28T19:31:48Z

lib/matplotlib/quiver.py

+            self.head_pos = 1.0
+        elif (head_pos == "mid") or (head_pos == "middle"):
+            self.head_pos = 0.5
+        elif type(head_pos) == float:


If you combine this into:

elif type(head_pos) == float and 0.0 < head_pos < 1.0:

then you only need the single final else to raise ValueError.

dopplershift · 2020-09-28T19:32:03Z

lib/matplotlib/quiver.py

+                                 "or a string in {'tail', 'middle', 'tip'}")
+        else:
+            raise ValueError("'head_pos' must be "
+                             "a value in the bounds 0head_pos<1,"


Typo: "0head_pos<1,"

github-actions · 2023-06-28T02:09:14Z

Since this Pull Request has not been updated in 60 days, it has been marked "inactive." This does not mean that it will be closed, though it may be moved to a "Draft" state. This helps maintainers prioritize their reviewing efforts. You can pick the PR back up anytime - please ping us if you need a review or guidance to move the PR forward! If you do not plan on continuing the work, please let us know so that we can either find someone to take the PR over, or close it.

melissawm · 2023-06-28T13:14:04Z

Hi @PipGrylls - are you interested in picking this back up? If you need help with the rebase or moving forward, please let us know!

PipGrylls · 2023-06-28T15:00:24Z

Hi, I won’t be picking this back up. I tried to fix the issues when I first pushed, happy for anyone to fix the minor bugs and finish the PR. Philip (Pip) Grylls, Dr ***@***.*** ***@***.***>

…

On 28 Jun 2023, at 14:14, Melissa Weber Mendonça ***@***.***> wrote: Hi @PipGrylls <https://github.com/PipGrylls> - are you interested in picking this back up? If you need help with the rebase or moving forward, please let us know! — Reply to this email directly, view it on GitHub <#15396 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AFOHDM273V7SQ5PFVLDL3XLXNQU2PANCNFSM4I63XHEQ>. You are receiving this because you were mentioned.

anntzer reviewed Oct 9, 2019

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timhoffm reviewed Oct 15, 2019

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examples/images_contours_and_fields/quiver_head_pos_demo.py Show resolved Hide resolved

QuLogic added status: needs rebase New feature labels Sep 25, 2020

PipGrylls added 8 commits September 25, 2020 08:41

modified quiver to allow for positioning of the arrowheads on the shaft

e89fc0f

adjusting example

e2808e8

removed mid_scale to add the feature to head pos, also made putting a…

a6fa90c

…n error outside the range thow a value error instead of defaulting to 0.5

added typecheck to headpos before doing GT/LT operation

24c4da8

resolving flake 8 issues

e66498a

removing debugging lines

aa44e32

added error to .flake8

ba6e421

heading marker length

1524d55

PipGrylls force-pushed the quiverdev branch from 2b2f39a to 1524d55 Compare September 25, 2020 07:44

PipGrylls added 2 commits September 25, 2020 08:58

Fixing line in quiver

621da10

Fixing flake errors

3c0088e

QuLogic reviewed Sep 25, 2020

View reviewed changes

PipGrylls and others added 6 commits September 28, 2020 07:43

Update examples/images_contours_and_fields/quiver_head_pos_demo.py

4e160ed

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

Update lib/matplotlib/quiver.py

a41ab8d

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

Update lib/matplotlib/quiver.py

93d8691

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

Update lib/matplotlib/quiver.py

670c203

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

removing 'mid scale

5490235

removing fixing commit

d975772

dopplershift requested changes Sep 28, 2020

View reviewed changes

jklymak added status: needs revision and removed status: needs rebase labels Dec 3, 2020

jklymak marked this pull request as draft December 3, 2020 15:29

github-actions bot added the status: needs rebase label Oct 18, 2022

github-actions bot added the status: inactive Marked by the “Stale” Github Action label Jun 28, 2023

rcomer added status: orphaned PR and removed status: inactive Marked by the “Stale” Github Action labels Jun 28, 2023

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Added arrowhead positioning options to quiver. #15396

Added arrowhead positioning options to quiver. #15396

PipGrylls commented Oct 9, 2019 •

edited

anntzer Oct 9, 2019

PipGrylls Oct 9, 2019

PipGrylls Oct 9, 2019

anntzer Oct 9, 2019 •

edited

PipGrylls Oct 9, 2019

timhoffm Oct 9, 2019

PipGrylls Oct 9, 2019

timhoffm commented Oct 14, 2019

QuLogic commented Sep 25, 2020

QuLogic Sep 25, 2020

QuLogic Sep 25, 2020

QuLogic Sep 25, 2020

QuLogic Sep 25, 2020

dopplershift Sep 28, 2020

dopplershift Sep 28, 2020

github-actions bot commented Jun 28, 2023

melissawm commented Jun 28, 2023

PipGrylls commented Jun 28, 2023 via email

		@@ -173,6 +174,15 @@

		'mid' is a synonym for 'middle'.

		head_pos : {'tail', 'mid', 'middle', 'tip'}, optional, default: 'tip'

Added arrowhead positioning options to quiver. #15396

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Added arrowhead positioning options to quiver. #15396

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PipGrylls commented Oct 9, 2019 • edited

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anntzer Oct 9, 2019 • edited

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timhoffm commented Oct 14, 2019

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github-actions bot commented Jun 28, 2023

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PipGrylls commented Jun 28, 2023 via email

PipGrylls commented Oct 9, 2019 •

edited

anntzer Oct 9, 2019 •

edited