Is there a classification of the type of data sets in machine learning problems? I am specifically interested in classification problems. I know a large number of algorithms like SVM, NN, Decision Trees, etc exist for classification problems.   I wonder if some properties of data set (like presence of natural clusters, number of training instances, type of input, etc) would give in-sights on which algorithm would work best for the problem.
When performing machine learning, the performance of the machine learning method is dependent on the original function $f$ that we are trying to learn (let's forget for a moment the non-deterministic error and focus on the properties of $f$).  I have a conceptual question. What would make a function easy to learn? For instance, a linear function can be easily learnt by linear methods such as linear regression and SVM. But in the general case, what would make a function easier to learn for decision trees or a neural network?   I believe feature engineering helps us move to a feature space in which the function we want to approximate is easier to represent. But what properties exactly are we trying to achieve for this function?
permission denied for root@localhost for ssh connection I just installed Ubuntu 14.04 and LAMP on that. Then, I wanted to configure my server, so tried out  tutorial.  When I give the command:  ssh root@localhost   I get : Permission denied, please try again. I have logged in as root user through the command :  sudo -i   I also tried the same, by logging in through:  sudo -s   I use the same password as that I used to log in as user, but still am getting the same error message.  Could someone help me out here?  PS: I looked into  but didn't seem to work for me. Is there a Google Drive client available? I'd like to install a  client for Xubuntu (12.04).  I'm getting non-English Google results, and I didn't find  in the Xubuntu repositories.   Does anyone know of a client that works well for Ubuntu or it's supported derivates (or installation instructions for grive?) I develop a windows application and am curious whether it works via Wine. The application runs fine with Wine but I get no sound. In fact, I'm not sure whether my ubuntu installation has MIDI capabilities. The sound output settings shows "LFE on Separate Mono Output" one with "no amplifier" and another with "amplifier". They both function. I am using Ubuntu 12.04 as a client on virtualbox that runs on windows 7.  Thanks for any suggestion!  EDIT: virtual box hosted by windows 7, ubuntu running as a client in virtualbox. Why $\sqrt{-1 \cdot {-1}} \neq \sqrt{-1}^2$? Exists a dedicated non-O(n²) Algorithm for avoiding to have overlapping elements? I am generating positions in a random fashion.  In the game world, instantiated elements have a radius, and shouldn't overlap.  The problem is that they will overlap because I use a usual random number generator combined with other fanciness. I can't use other random number generation algorithms where I can guarantee that the elements will never overlap.  A way to solve this is to use a spatial data structure and search for the nearest neighbors in that tree. When I insert an element into that tree, I update it accordingly.  This solution would do the work and it would be fast but my question is:  Is there a dedicated algorithm without that Tree implementation complexity which is faster than O(n²)? Is there any way to use a nether portal to travel to y = 250? This is a question in general, not specific to any method or data set. How do we deal with a class imbalance problem in Supervised Machine learning where the number of 0 is around 90% and number of 1 is around 10% in your dataset.How do we optimally train the classifier.  One of the ways which I follow is sampling to make the dataset balanced and then train the classifier and repeat this for multiple samples.   I feel this is random, Is there any framework to approach these kind of problems. Change installed AppleScript version What length of rope should be used to tie a cow to an exterior fence post of a circular field so that the cow can only graze half of the grass within that field?  updated: To be clear: the cow should be tied to a post on the exterior of the field, not a post at the center of the field. My 1.12 solution can be found . When trying to update command blocks to 1.13, I have the following:  scoreboard objectives add invert dummy   (run at start) then:  scoreboard players set FakePlayer invert 1   (impulse unconditional repeat) chained into:  execute at @e[tag=summoned] run scoreboard players reset FakePlayer invert   (chain unconditional repeat) chained into:  execute if score FakePlayer invert = 1 invert run say "All summoned animals are dead!"   This should reset FakePlayers score continuously until all entities with tag "summoned" are dead, then it should run the final condition. This does not happen, and I can't see why. I can't seem to find a satisfactory answer to this anywhere on the web. While  poses a related question, I don't think it sufficiently answers mine...  During the opening chapters of Jedi Search, Luke addresses the new Senate on the need to find new Jedi talent, or Force sensitive individuals. During this proposal, he cites that the most fruitful leads of Jedi potential are in the descendants of Jedi Knights: as Force sensitivity is hereditary. The book even discusses the notion that Leia should be comparatively well attuned to the Force, due to her being the child of Anakin Skywalker.  I understand that the concept of the Jedi as a totally celibate and monastic order was something that was retconned into the lore after Episode II: Attack of the Clones, and that there are examples of entire nuclear Jedi families exist (such as Andur Sunrider and Plo Koon)...  But if Force-manipulative ability is passed down genetically (as a potentially mutative property of their genetic makeup), why would the Jedi order be so numerous if they practice Chastity?  Even if procreation is not expressly forbidden (as in the pre-retcon Expanded Universe): why would Jedi need special permission to produce more Jedi potential children?  How are more Jedi created, if not through procreation? Has their profusion been deliberately retarded, and if so why? is there another explanation for their (pre-empirical) plenitude? I need to add a coloured line before my caption; this is what I used:  \usepackage[labelfont=bf]{caption}  \DeclareCaptionFormat{myformat}{\hrulefill #1  #2 #3} \captionsetup[figure]{format=myformat}   but the figure turns out to be line this:    and not a horinzontal line which what I want  2) I want the line to be coloured RGB [152 204 204] with thickness about the same as \top rule. Can anyone show me how to do this? I had to write the proof to show that an Ideal $P$ of a commutative ring $R$ is prime Ideal if $R/P$ is an integral domain.       let $a,b\in R$ s.t. $ab\in P$ ,        $$ab+P=P\implies(a+P)(b+P)=P\implies\overline a \overline b=0$$  and as $R/P$ is an integral domain either $a=0$ or $b=0$ $\implies a+P=P$ or  $b+P=P$.        $\therefore$ either $a\in P$ or $b\in P$.   Hence, $P$ is a prime Ideal.    Am I correct in writing this or am I making some error... Line numbering paragraph oriented? I'm using the lineno package with the pagewise option but I need a way to get the numbering restart every paragraph break. I need a general solution to pass to the latex command, e.g.:  latex "\AtBeginDocument{\RequirePackage[pagewise]{lineno}\linenumbers}\input{mydocument.tex}"   I read the lineno manual but the package does not provide this feature. Is there any trick to do that? How can I create Light Streaks in Cycles? Is it correct to use Bernoulli's theorem to explain that a disk floats in the air? Should the correct explanation be based on Boyle's law? In this video, a device is introduced from 1 minute to 18 seconds. After entering the air, the disc at the bottom of the device will be suspended in the air. The video explains that this is because of the Bernoulli effect, but I think this explanation is incorrect, because the disc gap, the radial volume is increasing. Therefore, the reason why the disk is suspended is that the air volume becomes larger, so the pressure decreases (according to Boyle's law). If the air moves along the radial direction at a constant speed, the volume of the air must be constantly increasing, right? So the pressure is decreasing, right? Is there a tool that combines zcat and cat transparently? When handling log files, some end up as gzipped files thanks to logrotate and others not. So when you try something like this:  $ zcat *   you end up with a command line like zcat xyz.log xyz.log.1 xyz.log.2.gz xyz.log.3.gz and then with:  gzip: xyz.log: not in gzip format   Is there a tool that will take the magic bytes, similar to how file works, and use zcat or cat depending on the outcome so that I can pipe the output to grep for example?  NB: I know I can script it, but I am asking whether there is a tool out there already. What is Java's answer to WPF? I'm mostly a .Net person at the moment, but I've been playing with Java some lately-- exploring what's out there.  Now I'm looking for the Java equivalent for WPF.  I know I could find an OpenGL library or two out there, but that's not really as rich or simple as the WPF system. Consider $\mathbb R^{[0,1]}$ the space of all functions from $[0,1]$  to $\mathbb R$  and the cylindrical sigma algebra $\mathcal B$  on it. The question is: how to prove that $C[0,1]\notin \mathcal B$. Why can't I install iOS 9.3? I saw an update for my iOS 9.2.1 device to iOS 9.3.  However, it said that the update cannot be verified, although it was downloaded.  I even deleted all data and applications from the device, but I still cannot update the device to 9.3; it just says "Your software is up to date" on iOS 9.2.1.  Can you force an update to 9.3?