Training a neural network (R)
What should I do when my neural network doesn't learn?
Install python packages for specific python version I understand that in Ubuntu 14.04, you have access to both python 2.7.6 and python 3.4.0. When getting python packages through the command line, how do I make sure that I am installing packages meant for python 2.7.6 and not for python 3.4.0? What does the fourth number in the release version mean? Invisible space when trying to remove file (but exclude all files in a list)? I'm trying to accomplish a simple task using the excellent post : I would like to remove all files from a folder except those listed in a .txt file contained in the folder. The syntax works fine, but for some reason all files are removed - basically the script is saying that there are no correspondences between the filenames in the folder and those in the .txt file - but I can see that there are!   I thought maybe there might be some invisible white space after my file names that I cannot see (in the folder or the .txt file). But I don't think so...Is there another solution that I am not thinking of? How to detect existence of a class using SFINAE? To which extent is general relativity a gauge theory? Special Relativity - Regarding the Simultaneity of Events During the Train Paradox My questions concerns that classic train paradox, wherein there is a train and a tunnel of equal length, and the train is traveling and some fraction of the speed of light towards the tunnel.  According to the Special Theory of Relativity, an observer outside the tunnel will see the train length contracted (Lorentz Contraction), whereas an observer inside will see the tunnel contracted.   Additionally, suppose that there were doors at the ends of the tunnel and that the observer outside the tunnel closed both doors instantaneously when he/she saw that the train was completely inside the tunnel.  The classic resolution of this paradox invokes the non-simultaneity of events, explaining that the observer in the train sees the far door close first, and then, once the train has begun to exit the tunnel, looks back to see the door at the beginning close. Thus, both observers agree that the train does not touch the door when they are closed for an instant.  Now my questions.  Why is it that the observer on the train sees the far door close first? It seems to me that the information coming from the far door would reach the observer on the train only after the information from the other door is reach.   Under this interpretation, the observer on the train would observe the train getting hit by the doors. What if, by some means, this event can be explained in terms of a stationary observer too? Everyone always concludes that the train remains untouched by the doors, but really the only condition that needs to be met is that both observers must agree. Why can't they both agree that the train was hit?  So, to summarize.   Why is the door that is farther away from the train observed to close first? Why can't the other possible conclusion (both see a hit train) be observed? I found this in . I've paraphrased for clarity.  There are 100 professors. Some are honest, while others are dishonest. There are more honest professors than dishonest ones. Honest professors always tell the truth, but the dishonest ones sometimes tell the truth and sometimes lie. You can ask any professor the following question about any other professor, "Professor Y, is Professor X honest?" to which he/she will answer yes or no. Design an algorithm that allows you to figure out which of the professors are honest with no more than 198 questions.  The bold part is the kicker. If liars always lied, then the problem is trivial - just ask 99 people about one guy. The majority would be the truthful answer, so you know your honest guys and your liars.  So, any advice? If you give the answer please put it in spoiler tags since I'm just looking for direction. Reading/writing an INI file Is there any class in the .NET framework that can read/write standard .ini files:  [Section] &lt;keyname&gt;=&lt;value&gt; ...   Delphi has the TIniFile component and I want to know if there is anything similar for C#? How can I get a reference to a method? Exam with 18pt main font What is the bug about: Keyword gets duplicated even when the query is not modified.  Impact: As far as i can tell - cosmetic.  How to replicate: Go to:  and keep pressing Search button. With each search there will be a duplicate python keyword appended to search box.  Best guess for what is causing it: I think you have somewhere a piece of code that appends tag as a keyword without checking if it is already present. My reasoning comes from this url:  not having the same issue - the tag is not present in it. How to line up the pieces at the coast near the shipwreck? In The Witness, I was walking along the coast, and I came upon this:    Now, since I've learned      that mazes can be embedded in the environment,   I see the puzzle here, but I just can't get the pieces to line up well enough.  Standing on the couch and walking all around it doesn't seem to get me a       functional maze.   Where do I need to stand to activate the puzzle successfully? Why is the decay of a neutral rho meson into two neutral pions forbidden? Why don't websites immediately display their text these days? I've noticed that recently many websites are slow to display their text. Usually, the background, images and so on are going to be loaded, but no text. After some time the text starts appearing here and there (not always all of it at the same time).  It basically works the opposite as it used to, when the text was displayed first, then the images and the rest was loading afterwards. What new technology is creating this issue? Any idea?  Note that I'm on a slow connection, which probably accentuates the problem.  See below for an example - everything's loaded but it takes a few more seconds before the text is finally displayed: Categorical Quotient and group actions I am trying to practice calculating categorical quotients and I ran into this example. I am unable to get the answer and was wondering if someone can help?  Let $G = Z/3Z =$ $\{1, \omega, \omega^2\}$, where $\omega$ is a cube root of unity. Let $G$ act on $𝔸^{2}$ via $\omega(x, y) = (\omega x, \omega y)$. Find the categorical quotient of $𝔸^{2}$ by G. Which of the following two sentences is correct?  He must decide who to be. He must decide whom to be.  I can think of arguments for both sides, but I'm not sure. To elaborate, is who(m) the object of decide, the subject of be, or the object of be? Does the infinitive form of be have any bearing on the answer? And is there anything else to consider about the position or role of who(m) in this particular sentence that would inform the answer? The answers to the linked question  say to &quot;substitute he and him for who and whom.&quot; However, that doesn't give a clear answer in this context, because neither of those pronouns sounds right: &quot;He must decide to be he&quot;? &quot;He must decide to be him&quot;? Normally we'd use a reflexive pronoun here (&quot;He must decide to be himself&quot;) and it's not clear what case that corresponds to. A financial planner treated us in a dismissive fashion and I want to say that he "gave us the back of his hand" but that phrase doesn't seem to have the meaning of dismissive. Does it or is there a similar idiom? Simple explanation to the induction from the slowly changing $\vec B$ of a solenoid in the region of $0$ magnetic field What does $dx$ mean? $dx$ appears in differential equations, such us derivatives and integrals.  For example, a function $f(x)$ its first derivative is $\dfrac{d}{dx}f(x)$ and its integral $\displaystyle\int f(x)dx$. But I don't really understand what $dx$ is. Achievements tab isn't working in Area 51 When I try to bring down the Achievements tab in Area 51, it's showing an error dialogue.  Strangely enough, the global inbox dropdown works just fine.  Could be connected to .  Screenshot: