Refactor rotation function.

[jcapriot]

Fixes issue #72.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 85.93%. Comparing base (179c191) to head (4d312cb).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
geoana/em/static/wholespace.py	50.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #78      +/-   ##
==========================================
+ Coverage   85.88%   85.93%   +0.04%     
==========================================
  Files          31       31              
  Lines        3139     3149      +10     
==========================================
+ Hits         2696     2706      +10     
  Misses        443      443              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.