{"action":"created","issue":{"url":"https://api.github.com/repos/ipython/ipython/issues/8327","labels_url":"https://api.github.com/repos/ipython/ipython/issues/8327/labels{/name}","comments_url":"https://api.github.com/repos/ipython/ipython/issues/8327/comments","events_url":"https://api.github.com/repos/ipython/ipython/issues/8327/events","html_url":"https://github.com/ipython/ipython/issues/8327","id":68947839,"number":8327,"title":"grayed out scrollbars appearing for long text markdown","user":{"login":"rlabbe","id":5308143,"avatar_url":"https://avatars.githubusercontent.com/u/5308143?v=3","gravatar_id":"","url":"https://api.github.com/users/rlabbe","html_url":"https://github.com/rlabbe","followers_url":"https://api.github.com/users/rlabbe/followers","following_url":"https://api.github.com/users/rlabbe/following{/other_user}","gists_url":"https://api.github.com/users/rlabbe/gists{/gist_id}","starred_url":"https://api.github.com/users/rlabbe/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rlabbe/subscriptions","organizations_url":"https://api.github.com/users/rlabbe/orgs","repos_url":"https://api.github.com/users/rlabbe/repos","events_url":"https://api.github.com/users/rlabbe/events{/privacy}","received_events_url":"https://api.github.com/users/rlabbe/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"milestone":{"url":"https://api.github.com/repos/ipython/ipython/milestones/28","html_url":"https://github.com/ipython/ipython/milestones/not%20ipython","labels_url":"https://api.github.com/repos/ipython/ipython/milestones/28/labels","id":1203441,"number":28,"title":"not ipython","description":"Milestone for issues open after 4.0 that no longer correspond to the ipython/ipython repo.\r\n\r\nThese may be migrated to their new homes.","creator":{"login":"minrk","id":151929,"avatar_url":"https://avatars.githubusercontent.com/u/151929?v=3","gravatar_id":"","url":"https://api.github.com/users/minrk","html_url":"https://github.com/minrk","followers_url":"https://api.github.com/users/minrk/followers","following_url":"https://api.github.com/users/minrk/following{/other_user}","gists_url":"https://api.github.com/users/minrk/gists{/gist_id}","starred_url":"https://api.github.com/users/minrk/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/minrk/subscriptions","organizations_url":"https://api.github.com/users/minrk/orgs","repos_url":"https://api.github.com/users/minrk/repos","events_url":"https://api.github.com/users/minrk/events{/privacy}","received_events_url":"https://api.github.com/users/minrk/received_events","type":"User","site_admin":false},"open_issues":39,"closed_issues":34,"state":"open","created_at":"2015-07-11T16:16:41Z","updated_at":"2015-12-16T12:08:15Z","due_on":null,"closed_at":null},"comments":7,"created_at":"2015-04-16T15:24:57Z","updated_at":"2015-12-16T12:08:15Z","closed_at":"2015-12-16T12:08:15Z","body":"Recently I've noticed that my notebooks are filled with inoperable scrollbars. Many of the cells have a grayed out scrollbar drawn beside it. All of the content is visible; scrolling is not required.  I've done some tests and with the same notebook they do not appear in IPython 3.0, but do appear with version 3.1.  This is in Chrome version 41, Windows 7 and Windows 8. I've not tested elsewhere.\r\n\r\nI've pasted an example below which includes text and latex for a markdown cell. However, the same thing is happening with code output.\r\n\r\n\r\n![image](https://cloud.githubusercontent.com/assets/5308143/7184278/5405f58e-e411-11e4-8757-4bb924f170b4.png)\r\n\r\nThis is the markdown for that cell\r\n\r\nNow we are prepared to compute the covariance matrix. The *covariance* measures how much two random variables move in the same direction, and is defined as\r\n\r\n$$ COV(x,y) = \\frac{1}{N}\\sum_{i=1}^N (x_i - \\mu_x)(y_i - \\mu_y)$$\r\n\r\nIf we compare this to the formula for the variance of a single variable we can see where this definition came from.\r\n\r\n$$\\sigma^2 = \\frac{1}{N}\\sum_{i=1}^N(x_i - \\mu)^2$$\r\n\r\nAnd indeed, the covariance of a variable with itself is just the variance of the variable, which we can trivially prove with\r\n\r\n$$\\begin{aligned}\r\nCOV(x,x) &= \\frac{1}{N}\\sum_{i=1}^N (x_i - \\mu_x)(x_i - \\mu_x) \\\\\r\n&= \\frac{1}{N}\\sum_{i=1}^N (x_i - \\mu_x)^2 \\\\\r\n&= VAR(x)\r\n\\end{aligned}$$\r\n\r\n\r\nLet's build some familiarity with this by calculating the covariance for the $\\mathbf{x}$ from the beginning of this section.\r\n\r\n$$\\mathbf{x}_0 = \\begin{bmatrix}1 \\\\8\\\\3\\end{bmatrix},\\ \\  \\mathbf{x}_1 = \\begin{bmatrix}3\\\\7\\\\7\\end{bmatrix}$$\r\n\r\nWe already know the mean is\r\n\r\n$$\\mu_x = \\begin{bmatrix}2\\\\7.5\\\\5\\end{bmatrix}$$"},"comment":{"url":"https://api.github.com/repos/ipython/ipython/issues/comments/165087422","html_url":"https://github.com/ipython/ipython/issues/8327#issuecomment-165087422","issue_url":"https://api.github.com/repos/ipython/ipython/issues/8327","id":165087422,"user":{"login":"minrk","id":151929,"avatar_url":"https://avatars.githubusercontent.com/u/151929?v=3","gravatar_id":"","url":"https://api.github.com/users/minrk","html_url":"https://github.com/minrk","followers_url":"https://api.github.com/users/minrk/followers","following_url":"https://api.github.com/users/minrk/following{/other_user}","gists_url":"https://api.github.com/users/minrk/gists{/gist_id}","starred_url":"https://api.github.com/users/minrk/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/minrk/subscriptions","organizations_url":"https://api.github.com/users/minrk/orgs","repos_url":"https://api.github.com/users/minrk/repos","events_url":"https://api.github.com/users/minrk/events{/privacy}","received_events_url":"https://api.github.com/users/minrk/received_events","type":"User","site_admin":false},"created_at":"2015-12-16T12:08:15Z","updated_at":"2015-12-16T12:08:15Z","body":"closing in favor of jupyter/notebook#735"}}