Its the only thing I'm missing, and I'm going crazy
No matter where I look, I just can't find gnome number [insert number here]. Where can I find every gnome in the game?
How to use measured step response to tune control system How does one use a measured step response to tune either a PID or convolution control scheme? Inspired by , I'm interested a more detailed explanation of how to implement a control system based on the measured step response.  I would not try to guess all the effects.  There are probably some non-obvious things going on, and you can't know all the parameters. I would measure the step response.  Find two pump settings that both result in the ball being within the measurable range within the tube.  Then have the controller suddenly switch from one setting to the other open loop.  Meanwhile measure what the ball does over time.  That is the step response.  You can take the derivative of that and get the impulse response.  From the impulse response you can predict the motion of the ball for any history of pump settings, assuming this is a linear system.  It is probably linear enough over the small range of settings to keep the ball within its normal range. You can use this as a simulation base to find the parameters for old fashioned PID control.  Or you can use the impulse response directly to do a convolution control.  You have to low pass filter the control input enough so that convolution kernel doesn't go negative unless your pump is actually reversible and can suck the ball back down.  How exactly does this work? ; I assume &quot;convolution control&quot; is the use of the pole-zero or transfer function, but don't see exactly how to get the parameters. RELATED:  * Since I started learning  and  last year, I've read a huge number of articles which insist that design patterns (especially in Java) are workarounds for the missing features in imperative languages. One article I found :     Most people I've met have read     by the Gang of   Four (GoF). Any self respecting programmer   will tell you that the book is   language agnostic and the patterns   apply to software engineering in   general, regardless of which language   you use. This is a noble claim.   Unfortunately it is far removed from   the truth.      Functional languages are extremely   expressive. In a functional language   one does not need design patterns   because the language is likely so high   level, you end up programming in   concepts that eliminate design   patterns all together.   The main features of functional programming (FP) include functions as first-class values, currying, immutable values, etc. It doesn't seem obvious to me that OO design patterns are approximating any of those features.  Additionally, in functional languages which support OOP (such as F# and OCaml), it seems obvious to me that programmers using these languages would use the same design patterns found available to every other OOP language. In fact, right now I use F# and OCaml every day, and there are no striking differences between the patterns I use in these languages vs. the patterns I use when I write in Java.  Is there any truth to the claim that functional programming eliminates the need for OOP design patterns? If so, could you post or link to an example of a typical OOP design pattern and its functional equivalent? Is it considered rude if you only ask Questions but almost never answer one yourself I have used the websites of SO a lot the past few months because I am busy with a large scale web project. I feel I get better answers here on SO than when I just do a Google search, maybe because I can be more specific here with my problem, and the responses are really fast.  Occasionally when I am not working I try to answer some questions, but the question almost always has an answer which is 'as good as' or 'better' than the answer I would supply.  So my question/answer ratio is about 20/1 something, if not more. When I look at my profile page I see a bucket-load of questions and almost nothing I answered myself.  Is this considered bad behaviour? I can see that this looks a little egoistic.  : One devoted to one's own interests and advancement. How can you explain that this double negation is not a double negation? Is there a rule in English about this kind of sentence?  PS / Do I have to mention Pink Floyd Copyright ? :-)  Edit : Since there are a lot of Pink Floyd related explanation, I'll bring a Freddy Mercury one : "I don't have time for no monkey business", which I also understand as "I don't have time for monkey business". Am I right ? Randomly populating procedural shape (or Image Texture) in Cycles TL;DR  How to take a shape or Image Texture and multiply it with random Location, Rotation and Scale along object:    Background  I have created my first procedural shape on my own from this function: $(x^2 + y^2 - 1)^3 - x^2y^3 = 0$   (big yay for math idiot)   Here is the result:    And I want to do something useful with it.  Research  I've tried to find something similar over the web (this is trending right now) and I'm surprised that this question wasn't asked before or I'm looking with wrong terms. I've tried random pattern, duplicating texture, populating image, random tiles, custom tiles and such. There is a lot about tiling textures but each and every Q&amp;A I've stumbled upon are about non overlapping ones. For example:            Tryout:  The only way I can think of this is to duplicate shape as a group and manually change values in Mapping Nodes:    As you can see this is... Well. Bad.  I've tried messing with Modulo, mixing Noise between vectors, using custom node groups for LocRotScale (thanks Gandalf) but results was none, thus nothing even to show.  Question  I want to populate this shape (or any other) along the object with random Location, Rotation and Scale - with control over its number/density and maybe variation strength.  Edit: I'm not looking for alternative methods of creating this setup such as Particles, Image Textures generated in 3rd party software, OSL shaders (CPU only) and such. My intention is to use this in procedural texture generation in Cycles with GPU support.  Blend file  Nothing really needed for this question but here - have this heart from me :) Properties vs Methods Quick question: When do you decide to use properties (in C#) and when do you decide to use methods?  We are busy having this debate and have found some areas where it is debatable whether we should use a property or a method. One example is this:  public void SetLabel(string text) {     Label.Text = text; }   In the example, Label is a control on a ASPX page. Is there a principle that can govern the decision (in this case) whether to make this a method or a property.  I'll accept the answer that is most general and comprehensive, but that also touches on the example that I have given. Flagging a deleted answer results in a message saying I am flagging too quickly What does this notification icon mean? Samsung s7 With services like Google Finance or Yahoo Finance it is very convenient to find the historical stock price metric of a listed company, but if the company is not listed, I can't find the data.  For example, I want to see the price metrics for Macromedia, which had been listed in 1993 on NASDAQ (MACR), then acquired by Adobe in 2005. How could I find its historical price metrics? Is there a such thing as an exchange program in Harry Potter? In the Harry Potter universe, is there any mention of an exchange student at Hogwarts or one of the Hogwarts students going on exchange at another school?  This happens all the time in the "muggle" school systems I'm sure it would happen in the wizarding schools as well. If $a,b$ are the roots of the equation $2 x^2 -3 x +1 = 0$, find an equation whose roots are $a/(2b +3)$, $b/(2a +3)$ If $a,b$ are the roots of the equation $2 x^2 -3 x +1 = 0$, find an equation whose roots are $a/(2b +3)$, $b/(2a +3)$   I was practicing quadratic equation questions online but I am stuck on this question.  I found the values of roots $a= 1$, $b= 1/2$ Duty Free in the USA. Why do I have to be given my purchase as I board the plane? I am not one for buying things in airports but recently my wife asked me to get her an alcoholic beverage while flying from the USA to Ireland (JFK-DUB). I made the purchase in JFK and was surprised to be told I had to collect it when departing for my flight as I board the plane. The sales assistant's English wasn't their best so I may have misheard and my Yorkshire twang may have thrown her, but I was somewhat surprised as to why I couldn't carry the bag myself to the plane.  Is there a law that prevents me from carrying my purchase to the plane or is this an added service I was charged, which I was duped into paying?  When boarding the plane there were several others who had to pick up their sealed duty free bags (why sealed?) so it wasn't just me. No explanation was given. Callout Mock Responses & multiple HTTP Status Code values I'm trying to unit test the behavior of some code which performs callouts and its logic is dependent on the HTTP status code of the response - 200 vs 401.  The pattern being exercised is familiar:   Make callout Response is (unauthorized) HTTP 401 Logic checks Status value on the response if (status == 200) { /* yay! */ } if (status == 401) { /* make request for auth /* }   retry original callout with newly acquired authorization yay!    I am attempting to test the code's "try, auth, retry" behavior using the MultiStaticResourceCalloutMock but it appears that only a single status code can be set for all requests that the mock provider can respond to using the .setStatusCode(int) method. Is this accurate?  Is there a mechanism for using a single MultiStaticResourceCalloutMock and having it respond with different status codes per URL in the test context?  Is the only solution here to use a Dispatcher such as what Andrew Fawcett documents here in this answer?   Is there another method/mechanism that allows for different status codes to be returned by the mock provider on the HTTPResponse?    Some  showing the one-time usage pattern of the .setStatusCode(200) method and the multimock class.  @isTest private class CalloutMultiStaticClassTest {     @isTest static void testCalloutWithMultipleStaticResources() {         // Use MultiStaticResourceCalloutMock to         // specify fake response for a certain endpoint and          // include response body in a static resource.             MultiStaticResourceCalloutMock multimock = new MultiStaticResourceCalloutMock();         multimock.setStaticResource(             'http://api.salesforce.com/foo/bar', 'mockResponse');         multimock.setStaticResource(             'http://api.salesforce.com/foo/sfdc', 'mockResponse2');         multimock.setStatusCode(200);         multimock.setHeader('Content-Type', 'application/json');          // Set the mock callout mode         Test.setMock(HttpCalloutMock.class, multimock);          // Call the method for the first endpoint         HTTPResponse res = CalloutMultiStaticClass.getInfoFromExternalService(             'http://api.salesforce.com/foo/bar');         // Verify response received          System.assertEquals('{"hah":"fooled you"}', res.getBody());          // Call the method for the second endpoint         HTTPResponse res2 = CalloutMultiStaticClass.getInfoFromExternalService(             'http://api.salesforce.com/foo/sfdc');         // Verify response received          System.assertEquals('{"hah":"fooled you twice"}', res2.getBody());     } } If a sequence converges in a metric space, it is Cauchy, and in $\mathbb{R}^k$ every Cauchy sequence converges.   Therefore, in $\mathbb{R}^k$ a sequence converges iff it is Cauchy.  Let $\{s_n\}$ be a sequence in $\mathbb{R}$ where each $s_n=\sum_{k=1}^na_k$. Therefore, by the above, every series converges iff  $$\left | \sum_{k=m}^n a_k\right| &lt;\epsilon$$ For a given $\epsilon &gt;0$ and an integer $N$ such that $N\le m\le n$. If $n=m$ then the statement reduces to:  A series converges if and only if $$|a_n| &lt; \epsilon $$ For a given $\epsilon &gt;0$ and an integer $N$ such that $N\le n$.  This clearly cannot be (e.g Harmonic series). When does the equivalence become an implication. How to permanently switch Caps Lock and Esc How can I permanently switch the Caps Lock and Esc key functions in Saucy? I can use this command to do it temporarily (until reboot):  /usr/bin/setxkbmap -option "caps:swapescape"   I tried adding that command as a Startup Application, but it doesn't seem to do anything. What is the limit of:  $$\lim_{n\to \infty} \frac{n^1+\dots+n^n}{1^n+\dots+n^n} = ?$$  I did some computation with big numbers, I guess it is in the interval $\left(\frac{1}{2},1\right)$. "There are no shortage of applications" I've been having an argument with a colleague about this sentence, could you please let me know which one of us is correct:     There are no shortage of applications for our product in this   space.   She is convinced that are should be replaced by is, and I think it should stand as it is. Thanks for your help! Are there any security risks using a single key-pair for both key-exchange and signing?  I'm mainly interested in using Curve25519 for key-exchange and Ed25519 for signing. But similar combinations, such as EC-DH and EC-Schnorr or even EC-DSA with the same key pair would be interesting too.   Curve25519 hashes the output of an x-coordinate only Diffie-Hellman key exchange Ed25519 is a slight variant of EC-Schnorr signatures.   I saw some recommendations to avoid using a single key for multiple purposes, but I couldn't find anything concrete. I have a dual boot of Windows 10 and Ubuntu 16.04. Recently I upgraded it to 18.04. As soon as I did it, it started showing DISK IS LIKELY TO FAIL SOON (37° C / 99° F).    I checked the status of my disk via Windows and it shows it’s perfectly healthy. I assumed the error occurred because my partition size of Ubuntu was 64GB (which I now increased to 86GB). Please help me out with this.    Edit: The results of smartctl - attributes How can I calculate this limit: $\lim\limits_{x\to 0} x\left\lfloor\frac{1}{x}\right\rfloor$? Calculate the following limit. $$ \lim_{x\to 0} x\left\lfloor\frac{1}{x}\right\rfloor $$ Where $\left\lfloor x \right\rfloor$ represents greatest integer function or floor function, i.e greatest integer less than or equal to $x$.  Thanks.