Support sawtooth excitation generation

[takenori-y]

No description provided.

[codecov]

Codecov Report

Merging #37 (ab8c2be) into master (5dcf5e8) will decrease coverage by 0.09%.
The diff coverage is 91.66%.

❗ Current head ab8c2be differs from pull request most recent head 1d37631. Consider uploading reports for the commit 1d37631 to get more accurate results

@@            Coverage Diff             @@
##           master      #37      +/-   ##
==========================================
- Coverage   99.83%   99.75%   -0.09%     
==========================================
  Files         155      155              
  Lines        3606     3616      +10     
==========================================
+ Hits         3600     3607       +7     
- Misses          6        9       +3     

Flag	Coverage Δ
unittests	99.75% <91.66%> (-0.09%)	⬇️

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Impacted Files	Coverage Δ
tests/test_excite.py	97.95% <88.88%> (-2.05%)	⬇️
diffsptk/core/excite.py	95.83% <100.00%> (-4.17%)	⬇️

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