GeezerVison is showing github.com — too much white space around Root Locus with omega-damping grid · Issue #1147 · python-control/python-control
too much white space around Root Locus with omega-damping grid #1147DescriptionWhen I turn on the omega-damping grid for root locus plot with grid=True (turned on by default), it adds too much white space around the actual plot, which is very annoying. With this grid turned off, plot is tight and nice.
I would like root locus to not have this extra white space around when grid is turned on, I am pretty sure this is some sort of platform-specific bug. Would appreciate any help 🙏
grid turned on (probably bug):
grid turned off (expected behavior):
Libraries:
- control 0.10.1
- matplotlib 3.10.0
I'm using python control in Google Colab. Activityslivingston commented on Apr 26, 2025 I cannot reproduce on the current tip of main branch, so this must have been fixed already. There is a new release coming soon: #1130 murrayrm commented on Apr 26, 2025 @slivingston Did you run inside a Jupyter notebook? What version?
I tried running this using the following versions and got the same problem as @datacurse noted:
IPython : 8.31.0
ipykernel : 6.29.5
ipywidgets : 8.1.5
jupyter_client : 8.6.3
jupyter_core : 5.7.2
jupyter_server : 2.14.2
jupyterlab : 4.3.3
nbclient : 0.10.1
nbconvert : 7.16.4
nbformat : 5.10.4
notebook : 7.3.1
qtconsole : not installed
traitlets : 5.14.3
I also tried running this on Colab and I get the same problem using the following commands:
!pip install git+https://github.com/python-control/python-control.git
import control as ct
import matplotlib.pyplot as plt
sys = ct.tf([1, 2], [1, 0, 0])
cplt = ct.root_locus(sys, grid=True)
slivingston commented on Apr 26, 2025 No, I ran it in IPython in a terminal, so the Matplotlib backend would be different. I just tried in Colab and reproduced it (like you), so now I think it is something new. roryyorke commented on Jul 11, 2026 With matplotlib 3.10.0, I can reproduce this. (Also happens in Colab, at time of writing, and Colab is also running matplotlib 3.10.0)
With matplotlib 3.11.0, there's no extra whitespace, but the damping grid lines look wrong.
Other installed packages at end; apologies for long list, I also installed jupyterlab.
matplotlib 3.10.0
matplotlib 3.11.0
packages
changing matplotlib versions didn't result in any upgrade or downgrade of other packages. This list is for matplotlib 3.11.0.
Package Version Editable project location
------------------------- ----------------------- ------------------------------
anyio 4.14.1
argon2-cffi 25.1.0
argon2-cffi-bindings 25.1.0
arrow 1.4.0
asttokens 3.0.1
async-lru 2.3.0
attrs 26.1.0
babel 2.18.0
beautifulsoup4 4.15.0
bleach 6.4.0
certifi 2026.6.17
cffi 2.1.0
charset-normalizer 3.4.9
comm 0.2.3
contourpy 1.3.3
control 0.10.3.dev20+g7d5019e0b /home/roryy/src/python-control
cycler 0.12.1
debugpy 1.8.21
decorator 5.3.1
defusedxml 0.7.1
executing 2.2.1
fastjsonschema 2.21.2
fonttools 4.63.0
fqdn 1.5.1
h11 0.16.0
httpcore 1.0.9
httpx 0.28.1
idna 3.18
ipykernel 7.3.0
ipython 9.15.0
ipython_pygments_lexers 1.1.1
isoduration 20.11.0
jedi 0.20.0
Jinja2 3.1.6
json5 0.15.0
jsonpointer 3.1.1
jsonschema 4.26.0
jsonschema-specifications 2025.9.1
jupyter_builder 1.1.0
jupyter_client 8.9.1
jupyter_core 5.9.1
jupyter-events 0.12.1
jupyter-lsp 2.3.1
jupyter_server 2.20.0
jupyter_server_terminals 0.5.4
jupyterlab 4.6.1
jupyterlab_pygments 0.3.0
jupyterlab_server 2.28.0
kiwisolver 1.5.0
lark 1.3.1
MarkupSafe 3.0.3
matplotlib 3.11.0
matplotlib-inline 0.2.2
mistune 3.3.3
nbclient 0.11.0
nbconvert 7.17.1
nbformat 5.10.4
nest-asyncio2 1.7.2
notebook 7.6.0
notebook_shim 0.2.4
numpy 2.5.1
packaging 26.2
pandocfilters 1.5.1
parso 0.8.7
pexpect 4.9.0
pillow 12.3.0
pip 25.1.1
platformdirs 4.10.0
prometheus_client 0.25.0
prompt_toolkit 3.0.52
psutil 7.2.2
ptyprocess 0.7.0
pure_eval 0.2.3
pycparser 3.0
Pygments 2.20.0
pyparsing 3.3.2
python-dateutil 2.9.0.post0
python-json-logger 4.1.0
PyYAML 6.0.3
pyzmq 27.1.0
referencing 0.37.0
requests 2.34.2
rfc3339-validator 0.1.4
rfc3986-validator 0.1.1
rfc3987-syntax 1.1.0
rpds-py 2026.6.3
scipy 1.18.0
Send2Trash 2.1.0
six 1.17.0
soupsieve 2.8.4
stack-data 0.6.3
terminado 0.18.1
tinycss2 1.5.1
tornado 6.5.7
traitlets 5.15.1
typing_extensions 4.16.0
tzdata 2026.3
uri-template 1.3.0
urllib3 2.7.0
wcwidth 0.8.2
webcolors 25.10.0
webencodings 0.5.1
websocket-client 1.9.0
roryyorke commented on Jul 12, 2026 control's grid.py defines ModifiedExtremeCycleFinder, subclassing matplotlib's angle_helper.ExtremeFinderCycle, and overrides __call__. ExtremeFinderCycle is a subclass of ExtremeFinderSimple.
Somewhere between matplotlib 3.10.0 and 3.11.0, matplotlib moved the extreme finder logic into _find_transformed_bbox, which is called by ExtremeFinderSimple's __call__, and _find_transformed_bbox is directly called in some places, e.g., GridFinder.get_grid_info. In control, _find_transformed_bbox is not overridden, so we're getting the "finder" behaviour of ExtremeFinderCycle.
See https://gist.github.com/roryyorke/655741c97b6bb6062f6fcb037151cac1/revisions for diff of grid_finder.py between 3.10.0 and 3.11.0 (this is "by-hand" created in Github gist; Github doesn't have easily accessible file-diff-between-version capability).
I did a cursory search of matplotlib's issues for ExtremeFinderSimple and _find_transformed_bbox, but nothing is mentioned. The docs for this corner of matplotlib are a bit thin.
Anyway, the fix on the control side is to move the calcs in ModifiedExtremeCycleFinder.__call__ to _find_transformed_bbox, and (to be confirmed) just omit the __call__ override.
That doesn't solve the extra whitespace question for Matplotlib 3.10.0, of course - I've hijacked the discussion around that a bit, sorry.
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