At which threshold is unbalanced data a problem for a binary classification tree?
When is unbalanced data really a problem in Machine Learning?
Using "that" and "this" interchangeably Modelling the number of apples an orchard yields with diminishing returns per tree This is   in the University of Washington's precal book.  Sylvia has an apple orchard. One season, her 100 trees yielded 140 apples per tree. She wants to increase her production by adding more trees to the orchard. However, she knows that for every 10 additional trees she plants, she will lose 4 apples per tree (i.e., the yield per tree will decrease by 4 apples). How many trees should she have in the orchard to maximize her production of apples?  Instructing a precal class, I walked through my approach to answering this in class (without preparing) and ended up doing something strange that may have confused the students. How would you clearly explain a way to get the function for the number of apples that we are trying to maximize? More generally, how would approach answering this question? It'd be nice to collect a some different approaches to demonstrate to my students that there is not a single rigid correct way to solve a problem. How do I make a floor plan with specific dimensions? How does the telepathy supernatural ability work? Jet stream of water I would like to simulate a stream of water like the one in the picture, but I don't know how to simulate the fast-moving, white water. Should I use particles to simulate foam or is it much better to concentrate in the material properties? Thanks Search only for the currently active language How can I restrict the results from a default search in Drupal 7, to bring only the nodes that are in the current language?  My website has a three language switcher; the user chooses what language he wants to use when viewing the site. If he searches something, the result page bring results from other languages. Today I have only 3 enabled languages, but we plan to expand this to 6 or more. How many Marvel Earths (Universes) are there? Ubuntu doesn't boot! Can file uploads time out in PHP? Hi im quite new to PHP, i have created a form for very large csv files to be uploaded to my server. Some one mentioned to me that the browser can time out due to the uploading file being to big, is this true? and if so, can it be prevented?  Thanks for your help! How to get text from an element , when getText fails I have the following element element(by.css(&quot;span[aria-label='Picker ID, TESTUSER']&quot;)  I want to assure the text on this filed is TESTUSER, so I tried:  expect(element(by.css(&quot;span[aria-label='Picker ID, TESTUSER']&quot;)).getAttribute('value')).toEqual('TESTUSER');  then I got the error: Expected null to equal 'TESTUSER' So I tried: element(by.css(&quot;span[aria-label='Picker ID, TESTUSER']&quot;)).getText().then(function (value) {         console.log(value);       })  And I got this error: Expected '' to be 'TESTUSER'.  How to get the value of this field and expect it is TESTUSER? Referencing List by indexVar in lightning component I have nested list in my lightning component and now I want  to refer records of list using indexVar.  Has anyone done this before?  &lt;aura:iteration items="{!v.records}" var="row" indexVar="rowCnt"&gt;  Like `{!row[rowCnt]}?`  &lt;/aura:iteration&gt; I currently have an ec2 &quot;t2.nano&quot; instance up and running. I would like to switch to a &quot;t2.micro&quot;. In order to do that, I need to stop the instance. But I would lose my IPv4 address in the process. And I do not want that (because I have several ssh tunnels up and running from rasps in the wild that are currently hard coded to connect to this IPv4 address). I decided to create an Elastic IP address. But I understand that by creating an Elastic IP address and assigning it to my current ec2 instance, I would lose my current IPv4 address too. Is it possible to create an Elastic IP address from the current IPv4 address of my ec2 instance? If so, how can I do this operation? Embed LaTeX math equations into Microsoft Word Let's say I have a (comparatively) lovely-looking document in LaTeX, full of lovingly typeset, (relatively) complex equations. Now, let's say some barbarians come along one day and decide that the document has to be put into Microsoft Word (2007). ...after the usual mourning period associated with such events, let's say I value my job (more specifically, the bread it provides) enough to get all the text and tables formatted and references organised into the Word document. –...related questions  and – Now I'm looking at the equations with fear and dread. One option of course is to just lift screenshots from the original document, but this is painstaking if I need to refer to parts of the equation in the text. Also, I might need to edit equations on the fly. Anyone know of a free application which allows embedding LaTeX math into MS Word? I've looked at  and  which do roughly what I want... they build LaTeX images from source and embed them into the Word document, allowing to edit the source later... but both are commerical. ...any help in these troubling times will be greatly appreciated. EDIT: Just a note that  offers a 30-day free trial and is working out really nicely... but still, it's not free. Might be a good solution for those with short-term needs, or money. $P(x) = 0$ is a polynomial equation having at least one integer root, where $P(x)$ is a polynomial of degree five and having integer coefficients.  If $P(2) = 3$ and $P(10)= 11$, then prove that the equation $P(x) = 0$ has exactly one integer root.  I tried by assuming a fifth degree polynomial but got stuck after that.  The question was asked by my friend. Setting up LVM Snapshot as a backup/restore point in ubuntu. Why? Well, as I see it, with all the great usefulness of Linux, its biggest drawback is with its mixed up way of installing apps. All the dlls go to one directory. All the configuration files to another. And the binaries are also put in a bunch. Yes, Windows works the same way more or less, but with the nature of system/server software installed on Linux, being that most of the software installed is only about 95% mature at any given time, messing up your system twice a month is very probable.. Of course, we can backup the system before and after each installation, but that takes a million years. System backups (as oppose to just data/files backup) requires you to turn off you computer and use some form of bootable live CD and a backup media. And, if the drive is more than 15% full, it might take a long time to do the backup, even with modern hardware. So, how can this be done? Efficient way to find $[\mathbb{Q}(\sqrt{5}, \sqrt{3}, \sqrt{2}): \mathbb{Q}(\sqrt{3}, \sqrt{2})]$ I want to show rigorously that this is 2. I'm sure there's a faster way than by trying to see if $\sqrt{5} = a + b \sqrt{2} + c \sqrt{3} + d \sqrt{6}$ (linear combination of the basis elements for $\mathbb{Q}(\sqrt{3}, \sqrt{2})$). I'm just not sure what. Composite primary key from multiple tables / multiple foreign keys I want to build a composite primary key made up of foreign keys from two different tables. I'm still pretty green to this...  A great answer was given to building a composite key from multiple foreign keys on  but I want to do this from multiple tables. I am using Oracle 11g.  foreign key (Name, BoughtFrom, TimeBought)    references the_other_table_name (Name, BoughtFrom, TimeBought)   Imagine that the "references" line actually includes multiple tables. I'm not even sure that the above syntax will work with Oracle.  I have one table "Student" and one table "Parent". It is a many-to-many relationship. My association table is named "Relation" and I would like to make a composite primary key from "PAR_ID" and "STU_ID". Both are foreign keys. Sharing Test code in Maven When is mapping $g$ to $g^{-1}$ a group homomorphism? It just means that the map maps the identity to the identity and inverses to inverses. So does that mean it's only a homomorphism if the inverse is itself? How is exponentiation defined in Peano arithmetic? How would exponentiation be defined in Peano arithmetic? Unless $n$ is fixed natural number, $x^n$ seems to be hard to define.   Edit 2: So, what would be the way to define $x^n+y^n = z^n$ using $\Sigma_1^0$ formula?  Edit: OK, I say Peano arithmetic has addition and multiplication stuffs. This allows additions to be expressed without quantifiers but as for exponentiation Peano arithmetic is silent. That's why I asked this question. Just for clarification.