{"action":"closed","issue":{"url":"https://api.github.com/repos/scipy/scipy/issues/8745","repository_url":"https://api.github.com/repos/scipy/scipy","labels_url":"https://api.github.com/repos/scipy/scipy/issues/8745/labels{/name}","comments_url":"https://api.github.com/repos/scipy/scipy/issues/8745/comments","events_url":"https://api.github.com/repos/scipy/scipy/issues/8745/events","html_url":"https://github.com/scipy/scipy/issues/8745","id":314772575,"number":8745,"title":"scipy.signal.chirp problem","user":{"login":"art4206","id":38438950,"avatar_url":"https://avatars3.githubusercontent.com/u/38438950?v=4","gravatar_id":"","url":"https://api.github.com/users/art4206","html_url":"https://github.com/art4206","followers_url":"https://api.github.com/users/art4206/followers","following_url":"https://api.github.com/users/art4206/following{/other_user}","gists_url":"https://api.github.com/users/art4206/gists{/gist_id}","starred_url":"https://api.github.com/users/art4206/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/art4206/subscriptions","organizations_url":"https://api.github.com/users/art4206/orgs","repos_url":"https://api.github.com/users/art4206/repos","events_url":"https://api.github.com/users/art4206/events{/privacy}","received_events_url":"https://api.github.com/users/art4206/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":3,"created_at":"2018-04-16T18:42:39Z","updated_at":"2018-04-16T19:32:15Z","closed_at":"2018-04-16T19:32:15Z","author_association":"NONE","body":"Scipy.signal.chirp produces strange looking frequency sweep - see figure and example code below.\r\n\r\n![figure_1](https://user-images.githubusercontent.com/38438950/38828458-c5abcaae-417b-11e8-941f-e053b743f51b.png)\r\n\r\n  Looking at the source code for Scipy.signal.chirp pasted below:\r\n           # 'phase' is computed in _chirp_phase, to make testing easier.\r\n           phase = _chirp_phase(t, f0, t1, f1, method, vertex_zero)\r\n           # Convert  phi to radians.\r\n           phi *= pi / 180\r\n           return cos(phase + phi)\r\n\r\nThe phase from _chirp_phase should be converted from degrees to radians for numpy.cos to work correctly.\r\n\r\n### Reproducing code example:\r\n```\r\nimport os\r\nimport numpy as N\r\nimport matplotlib.pyplot as plt\r\nfrom scipy.signal import chirp\r\n\r\nfStart = 5\r\nfStop = 10005\r\nscanTime = (8 * 60.)\r\nfCycles = (fStop-fStart)/scanTime\r\nnumPoints = 600000\r\nstepTime = scanTime/numPoints\r\nt = N.linspace(0, scanTime, numPoints)\r\npulseSeq = chirp(t, f0=fStart, f1=fStop, t1 = scanTime, method = 'linear')\r\nplt.plot(t,pulseSeq)\r\nplt.show()\r\n\r\n```\r\n\r\n### Error message:\r\n```\r\nThe phase from _chirp_phase should be converted from degrees to radians for numpy.cos to work correctly.\r\n```\r\n\r\n### Scipy/Numpy/Python version information:\r\n```\r\n('1.0.0', '1.14.0', sys.version_info(major=2, minor=7, micro=14, releaselevel='final', serial=0))\r\n```\r\n\r\n"}}
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