{"action":"opened","issue":{"url":"https://api.github.com/repos/Statistical-Connectomics-Sp15/intro/issues/72","labels_url":"https://api.github.com/repos/Statistical-Connectomics-Sp15/intro/issues/72/labels{/name}","comments_url":"https://api.github.com/repos/Statistical-Connectomics-Sp15/intro/issues/72/comments","events_url":"https://api.github.com/repos/Statistical-Connectomics-Sp15/intro/issues/72/events","html_url":"https://github.com/Statistical-Connectomics-Sp15/intro/issues/72","id":57380985,"number":72,"title":"Positive Definite Matrices","user":{"login":"whock","id":10751093,"avatar_url":"https://avatars.githubusercontent.com/u/10751093?v=3","gravatar_id":"","url":"https://api.github.com/users/whock","html_url":"https://github.com/whock","followers_url":"https://api.github.com/users/whock/followers","following_url":"https://api.github.com/users/whock/following{/other_user}","gists_url":"https://api.github.com/users/whock/gists{/gist_id}","starred_url":"https://api.github.com/users/whock/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/whock/subscriptions","organizations_url":"https://api.github.com/users/whock/orgs","repos_url":"https://api.github.com/users/whock/repos","events_url":"https://api.github.com/users/whock/events{/privacy}","received_events_url":"https://api.github.com/users/whock/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-02-11T21:36:21Z","updated_at":"2015-02-11T21:36:21Z","closed_at":null,"body":"When generating random matrices to serve as the adjacency matrix for a graph, I sometimes get an error where kmeans fails to run(scipy.cluster.vq.kmeans2 if that matters). The error message is \"Matrix is not positive definite.\" I looked up this term online but am still a bit confused - so what makes a matrix positive definite and why is this necessary for kmeans to run? Thanks "}}