René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Freqplot improvements introduced warning messages in tests","articleBody":"It looks like PR #522 introduced some warning messages in our GitHub Action tests:\r\n```\r\ncontrol/tests/freqresp_test.py::test_discrete[tf-0.1]\r\ncontrol/tests/freqresp_test.py::test_discrete[tf-0.1]\r\ncontrol/tests/freqresp_test.py::test_discrete[tf-True]\r\ncontrol/tests/freqresp_test.py::test_discrete[tf-True]\r\n  /home/runner/work/python-control/python-control/control/xferfcn.py:310: RuntimeWarning: divide by zero encountered in true_divide\r\n    out[i][j] = (polyval(self.num[i][j], x) /\r\n\r\ncontrol/tests/freqresp_test.py::test_discrete[tf-0.1]\r\ncontrol/tests/freqresp_test.py::test_discrete[tf-0.1]\r\ncontrol/tests/freqresp_test.py::test_discrete[tf-True]\r\ncontrol/tests/freqresp_test.py::test_discrete[tf-True]\r\n  /home/runner/work/python-control/python-control/control/xferfcn.py:310: RuntimeWarning: invalid value encountered in true_divide\r\n    out[i][j] = (polyval(self.num[i][j], x) /\r\n```\r\nI'm not quite sure what is generating the warnings, but it would be good to get rid of them if we can.\r\n\r\nTest results here: https://github.com/python-control/python-control/pull/522/checks\r\n\r\n@sawyerbfuller Any ideas?","author":{"url":"https://github.com/murrayrm","@type":"Person","name":"murrayrm"},"datePublished":"2021-02-08T05:36:28.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/538/python-control/issues/538"}