It seems errorbar caps currently do not account for a changed orientation due to theta_zero_location nor due to theta_zero_direction. Their angle stays the same as for the unmodifed plot.

The fix (add appropriate sign and offset) should likely be around here:

This is a good first issue, because the fix is straight forward and easy to verify.

Good first issue - notes for new contributors

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I’d love to give this issue a try and work on the fix!

@johnsonhsiung Got for it!

Tipp: use PolarAxes.get_theta_offset and PolarAxes.get_theta_direction to obtain the relevant numbers to include into the calculation.

I ran into a problem while trying to setup. I'm currently following this guide: https://matplotlib.org/devdocs/devel/contribute.html

While running this command
python -m pip install --no-build-isolation --editable .[dev]

I got this error which was an easy fix by running pip install ninja.
meson-python: error: Could not find ninja version 1.8.2 or newer.

However, after running again the command again, I was hit with a longer error

Obtaining file:///E:/opensource/matplotlib
  Checking if build backend supports build_editable ... done
  Preparing editable metadata (pyproject.toml) ... error
  error: subprocess-exited-with-error

  × Preparing editable metadata (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> [22 lines of output]
      + meson setup E:\opensource\matplotlib E:\opensource\matplotlib\build\cp312 -Dbuildtype=release -Db_ndebug=if-release -Db_vscrt=md --native-file=E:\opensource\matplotlib\build\cp312\meson-python-native-file.ini
      The Meson build system
      Version: 1.5.2
      Source dir: E:\opensource\matplotlib
      Build dir: E:\opensource\matplotlib\build\cp312
      Build type: native build
      Program python3 found: YES
      Project name: matplotlib
      Project version: 0.1.0.dev51091+g69f09d1
      C compiler for the host machine: gcc (gcc 6.3.0 "gcc (MinGW.org GCC-6.3.0-1) 6.3.0")
      C linker for the host machine: gcc ld.bfd 2.28
      C++ compiler for the host machine: c++ (gcc 6.3.0 "c++ (MinGW.org GCC-6.3.0-1) 6.3.0")
      C++ linker for the host machine: c++ ld.bfd 2.28
      Host machine cpu family: x86
      Host machine cpu: x86
      Program python found: YES (E:\opensource\matplotlib\myenv\Scripts\python.exe)
      Need python for x86, but found x86_64
      Run-time dependency python found: NO (tried sysconfig)

      ..\..\meson.build:37:14: ERROR: Python dependency not found

      A full log can be found at E:\opensource\matplotlib\build\cp312\meson-logs\meson-log.txt
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

I tried looking around online and was told to install from these two sites:

1. https://sourceforge.net/projects/mingw/
2. https://developer.arm.com/downloads/-/gnu-rm

I installed them, deleted my virtual env, and repeated the steps, but still receive the same error. Any ideas on how to proceed?
Thank you!

Also, here's the full log: meson-log.txt

Sorry, I cannot help setting up the compiler infrastructure on Windows. That's not my OS for development.

You may alternatively try GitHub Codespaces so that you don't have to do any local setup:

I'd like to work on this issue if possible! Newcomer so I may need some assistance.

Hope that this resolves the issue!

@vas1l if the answers aren't in the following docs, please let us know:

• https://matplotlib.org/devdocs/devel/contribute.html#how-to-pull-request
• https://matplotlib.org/devdocs/devel/testing.html#writing-a-simple-test

Removed the Good first issue label. Partly in hope to not attract any more duplicate PRs, but also because I think the discussion in #28905 is beyond the first issue level!