my internal speakers on my macbook pro just stopped working, they have disappeared from the sounds preferences control panel. the only option is 'optical digital outport'  the headphones still work, but there's a red light coming out of the headphone jack  help?
The volume on my macbook pro has suddenly become greyed out. I haven't installed any updates or made any modifications to the computer, it just suddenly became greyed out after waking the macbook up from sleeping.  I've tried resetting the PRAM, but I don't hear any chime at all when I start up my computer, no matter how long I wait/how many times the computer re-restarts itself.  There also seem to be no internal speakers detected when I go into system preferences. For both input and output the computer detects 0 devices.  Thanks so much in advance for any help!!
How to use xcolor to color a pgfplot How do I use xcolor to color a specific cell from a table in pgfplots? Is xcolor the best tool to use here? I'm trying to loop over a list of colors and color the cells in the column individually.  \documentclass{article} \usepackage{pgfplotstable,filecontents} \RequirePackage{listofitems} \usepackage{}  \begin{filecontents*}{test.csv}     ColA, ColB, ColC     0.17, 0.91, 0.67     0.15, 0.17, 0.92     0.48, 0.1, 0.28 \end{filecontents*}     \begin{document}     \pgfplotstabletypeset[col sep=comma,     ]{test.csv}     \def\mylistOne{green, blue, orange}     \readlist*\mylistTwo{\mylistOne}     \newcounter{myCounter}     \setcounter{myCounter}{-1}     \foreachitem\x\in\mylistTwo[]{         \stepcounter{myCounter}         \pgfplotstableset{             every row \themyCounter column 1/.style={                 \cellcolor{\x}         }     } } \end{document} How to combine array items with string substitution? Is there any way to favorite/bookmark an answer? Lots of questions are very generic, &quot;share an experience&quot; kinds of questions. In these cases, I am quite often interested in specific answers that may not have gotten that many upvotes. These questions also tend to elicit lots of responses, so going back to find the answers I'm interested in somewhere in the middle of a sea of responses is a pain. Is there a way to favorite or bookmark these answers? Can I request the code behind a research paper from the author? Update help center article on search to reflect the new position of the search box The page  says:      Enter search terms in the search box that appears in the upper right corner of every page    But the box is not there. Why didn't Dumbledore just hunt Voldemort down? Why are some faces in my mesh darker? While rendering a mesh with smooth shading on, I get a dark region/shadow on certain faces. The effect is more evident when smooth shading is applied to a mesh containing ngons, with the ngons turning black when rendered.   The blackening effect is visible in the viewport too.  How can I solve this problem? What is happening here, when I use squared loss in logistic regression setting? I am trying to use squared loss to do binary classification on a toy data set. I am using mtcars data set, use mile per gallon and weight to predict transmission type. The plot below shows the two types of transmission type data in different colors, and decision boundary generated by different loss function. The squared loss is $\sum_i (y_i-p_i)^2$ where $y_i$ is the ground truth label (0 or 1) and $p_i$ is the predicted probability $p_i=\text{Logit}^{-1}(\beta^Tx_i)$. In other words, I am replace logistic loss with squared loss in classification setting, other parts are the same. For a toy example with mtcars data, in many cases, I got a model &quot;similar&quot; to logistic regression (see following figure, with random seed 0).  But in somethings (if we do set.seed(1)), squared loss seems not working well.  What is happening here? The optimization does not converge? Logistic loss is easier to optimize comparing to squared loss? Any help would be appreciated.  Code d=mtcars[,c(&quot;am&quot;,&quot;mpg&quot;,&quot;wt&quot;)] plot(d$mpg,d$wt,col=factor(d$am)) lg_fit=glm(am~.,d, family = binomial()) abline(-lg_fit$coefficients[1]/lg_fit$coefficients[3],        -lg_fit$coefficients[2]/lg_fit$coefficients[3]) grid()  # sq loss lossSqOnBinary&lt;-function(x,y,w){   p=plogis(x %*% w)   return(sum((y-p)^2)) }  # this random seed is important for reproducing the problem set.seed(0)  x0=runif(3) x=as.matrix(cbind(1,d[,2:3])) y=d$am opt=optim(x0, lossSqOnBinary, method=&quot;BFGS&quot;, x=x,y=y)  abline(-opt$par[1]/opt$par[3],        -opt$par[2]/opt$par[3], lty=2) legend(25,5,c(&quot;logisitc loss&quot;,&quot;squared loss&quot;), lty=c(1,2)) From injective map to continuous map Why can't Python's raw string literals end with a single backslash? Space Expansion vs. Relative Motion Given 2 objects moving at some velocity $v$ relative to one another, is it possible to determine whether they are moving or whether the space between them is expanding? Why do only Hobbits use a combination of first- and last names? While all the Hobbits I can think of have a combination of first- and lastname (e.g., Bilbo Baggins, Peregrin Took, the Sackville-Baggins's,...), I can't think of any character* of another race that has a lastname:   Men seem to like to add a reference to their ancestors (e.g., Aragorn, Arathorn's son or Isildur's heir) Dwarves seem to like descriptive or honorary names (e.g., Thorin Oakenshield, Dain Ironfoot). They are not lastnames though, since they do not get passed on to descendants. Elves don't have a need for lastnames, since elvish names are unique. Some nevertheless seem to have an additive (e.g., Legolas Greenleaf). Likewise, I can't find any usage of lastnames among Ents, Eagles, Istari, Orcs, trolls,...   But why would a society that is quite rural and not a leader of modernization be the only one to use a modern naming system with first- and lastnames?  *Except for Tom Bombandil. But he is, well, "special". Why is Newton's first law necessary? Newton's second law says $F=ma$. Now if we put $F=0$ we get $a=0$ which is Newton's first law. So why do we need Newton's first law ?   Before asking I did some searching and I got this: Newtons first law is necessary to define inertial reference frame on which the second law can be applied.  But why can't we just use Newton's second law to define an inertial frame? So if $F=0$ but $a$ is not equal to 0 (or vice versa), the frame is non-inertial.  One can say (can one?) we cannot apply the second law to define a reference frame because it is only applicable to inertial frames. Thus unless we know in advance that a frame is inertial, we can't apply the second law.  But then why this is not the problem for the first law?  We don't need to know it in advance about the frame of reference to apply the first law. Because we take the first law as definition of an inertial reference frame.  Similarly if we take the second law as the definition of an inertial frame, it should not be necessary to know whether the frame is inertial or not to apply the second law (to check that the frame is inertial). How can I get more of this macro photo in focus? I understand Big-O notation, but I don't know how to calculate it for many functions. In particular, I've been trying to figure out the computational complexity of the naive version of the Fibonacci sequence:  int Fibonacci(int n) {     if (n &lt;= 1)         return n;     else         return Fibonacci(n - 1) + Fibonacci(n - 2); }   What is the computational complexity of the Fibonacci sequence and how is it calculated? Is it bad to marinate meat for too long? From my experience it is always best to marinate meat for a decent amount of time, so the meat can "soak" up the marinade and be more flavourful.  However, I came across this recipe here:   In the directions, it says: Add pork and marinade for a minimum of 6 hours or overnight, but no longer than 12 hours.  I was wondering, why does it say "no longer than 12 hours"? Isn't it good to let meat marinate for as long as possible?  Thanks. Assuming convergence of the following series, find the value of $\sqrt{6+\sqrt{6+\sqrt{6+...}}}$ Assuming convergence of the following series, find the value of $\sqrt{6+\sqrt{6+\sqrt{6+...}}}$  I was advised to proceed with this problem through substitution but that does not seem to help unless I am substituting the wrong parts. If i substitute the $6$, well then i am just stuck with above.   Any ideas on how to proceed. Also, what is the purpose of stating that it is convergent. Equation of a rectangle I need to graph a rectangle on the Cartesian coordinate system. Is there an equation for a rectangle? I can't find it anywhere. Conjectures Involving floor(x)/piecewise continuity with regards to Integration and Differential Equations [This answer has been heavily edited in response to a long chain of comments on Eric Stucky's answer.]  I came up with these few theorems and I am curious whether or not my hypothesis are true. I don't really have a method for proving these, mind you. I'm more considering these as things I've noticed to be true. I just don't know whether they are always true.  Some of these are definitions to which I will append "def." to the end of the title. Think of these as a given. It's like how the integral is defined abstractly as area. I'm defining terms.  Jump Series Theorem def.  A function $f$ [consisting of floor] is said to have a jump series if there is a series $\Sigma=\sum_{n=1}^\infty a_nH_n$ of scaled step functions such that $f+\Sigma$ no longer has any discontinuity attributable to floor. The sequence of scaling factors $a_n$ is called the jump sequence for the function.  Definition of Implied Derivative def.  We define the evaluation of the implied derivative of a function $y$ at the point $x$ as the set of values $y^{\to}(x) = \{y | y = \lim_{h \to 0^+} \frac {y(x+h) - f(h)}{h} \lor y = \lim_{h \to 0^-} \frac {y(x+h) - f(h)}{h}\}$. It is in this sense that the implied derivative has the potential of being a multi-valued operator.  Jump Series Resolution Theorem  [The original wording is preserved; I have a formalism but it assumes that having a jump function is equivalent to being piecewise continuous, which I'm not sure is true.]   The integral of a floor-based function is floor treated as a constant minus the appropriate jump series of the integral.  Integration Continuity Theorem  The (ordinary) indefinite integral of any function $f$ having a jump series must be continuous (or fixably discontinuous) on the domain of $f$. However, this can vary for the implied indefinite integral.  Calculus Jump Theorem def.  [Again, the original wording is preserved; the meaning of this phrase has not been properly illuminated]  Any form of jumping within a function representable as a floor function can be considered as a portion of the constant of the implied integration for floor.  Jump Location Theorem  For any function $a(x)$ with a jump series, the function $\lfloor a(x)\rfloor$, has points of discontinuity precisely at those $x$ such that $a(x) - [a(x)] = 0$.  Composite Floor Function Jump Sequence Theorem One  If $a$ is a function such that $a(x) - \lfloor a(x) \rfloor = 0$ when $x - \lfloor x \rfloor = 0$, then the jump sequence of the composite function $f(x - \lfloor a\rfloor)$ is a constant value $f(0) - f(1)$.  Implied Differential Equations Conjecture  Any continuous solution to an equation constructed with implied derivatives of various orders is the same as the solution to the similarly constructed differential equation. Adding grouped icons to favorite bar in Ubuntu 18.04 Is there anyway to add icons groups to the favorites bar aka Ubuntu dock (something like drawers or unity-launcher-folders) in Ubuntu 18.04 ?