{"action":"created","issue":{"url":"https://api.github.com/repos/mne-tools/mne-python/issues/1902","labels_url":"https://api.github.com/repos/mne-tools/mne-python/issues/1902/labels{/name}","comments_url":"https://api.github.com/repos/mne-tools/mne-python/issues/1902/comments","events_url":"https://api.github.com/repos/mne-tools/mne-python/issues/1902/events","html_url":"https://github.com/mne-tools/mne-python/issues/1902","id":64053204,"number":1902,"title":"FIX: whitening / rank issue when combining ","user":{"login":"dengemann","id":1908618,"avatar_url":"https://avatars.githubusercontent.com/u/1908618?v=3","gravatar_id":"","url":"https://api.github.com/users/dengemann","html_url":"https://github.com/dengemann","followers_url":"https://api.github.com/users/dengemann/followers","following_url":"https://api.github.com/users/dengemann/following{/other_user}","gists_url":"https://api.github.com/users/dengemann/gists{/gist_id}","starred_url":"https://api.github.com/users/dengemann/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/dengemann/subscriptions","organizations_url":"https://api.github.com/users/dengemann/orgs","repos_url":"https://api.github.com/users/dengemann/repos","events_url":"https://api.github.com/users/dengemann/events{/privacy}","received_events_url":"https://api.github.com/users/dengemann/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":2,"created_at":"2015-03-24T17:25:19Z","updated_at":"2015-03-24T20:22:03Z","closed_at":null,"body":"Apparently there is an issue with whitening and cov computation if multiple SSSed runs are considered in which the numbe of components dffer. Let's say over 10 runs we have a component range of 67-71 and then compute the covariance on epochs that include data from all these runs. The covariance spectrum would indicate a rank of 91, irrespective of the method used (e.g. empirical), but clearly the resulting whitening would look inappropriate. Contrastingly, when computed runwise, the rank of the cov would reflect the number of SSS components in that run.\r\n\r\nAny intuition? @Eric89GXL @agramfort @mshamalainen @LauriParkkonen "},"comment":{"url":"https://api.github.com/repos/mne-tools/mne-python/issues/comments/85677242","html_url":"https://github.com/mne-tools/mne-python/issues/1902#issuecomment-85677242","issue_url":"https://api.github.com/repos/mne-tools/mne-python/issues/1902","id":85677242,"user":{"login":"agramfort","id":161052,"avatar_url":"https://avatars.githubusercontent.com/u/161052?v=3","gravatar_id":"","url":"https://api.github.com/users/agramfort","html_url":"https://github.com/agramfort","followers_url":"https://api.github.com/users/agramfort/followers","following_url":"https://api.github.com/users/agramfort/following{/other_user}","gists_url":"https://api.github.com/users/agramfort/gists{/gist_id}","starred_url":"https://api.github.com/users/agramfort/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/agramfort/subscriptions","organizations_url":"https://api.github.com/users/agramfort/orgs","repos_url":"https://api.github.com/users/agramfort/repos","events_url":"https://api.github.com/users/agramfort/events{/privacy}","received_events_url":"https://api.github.com/users/agramfort/received_events","type":"User","site_admin":false},"created_at":"2015-03-24T20:22:03Z","updated_at":"2015-03-24T20:22:03Z","body":"indeed the intuition is that the head position is different for each run so\nthe SSS signal subspace is sightly different and artificially increases the\nnumerical rank of the data.\n\nnot sure what to do in this case besides allowing to specify the rank\nmanually. Or fix head position...\n"}}