Add a new property to an object property
How can I merge properties of two JavaScript objects dynamically?
How do I set up SIP voice calling in Empathy? I would like to use Empathy for Internet voice chat, but I do not see an option under the Empathy Accounts menu to create a SIP account.  How do I set up Internet voice calling in Empathy? How to show (raise) all windows of an application? When using divs when is it best to use a class vs id?   Is it best to use class, on say font variant or elements within the html? Then use id for the structure/containers?   This is something I've always been a little uncertain on, any help would  be great. I'm trying to understand the derivation of the equations for the logistic regression. I'm following the cs229 notes:    At some point in the derivation, in the notes we need to maximize the log-likelihood of the parameters:  ℓ(θ) = log L(θ) = y log h(x) + (1 - y) log(1-h(x))  In the notes, after the derivation we get:  $\frac{\partial}{\partial \theta_j}$ = (y $\frac 1 {h(x)}$ - (1 - y) $\frac 1 {1 - h(x)}$) $\frac{\partial}{\partial \theta_j}$h(x)  Shouldn't this be:  $\frac{\partial}{\partial \theta_j}$ = (y $\frac 1 {h(x)}$ + (1 - y) $\frac 1 {1 - h(x)}$) $\frac{\partial}{\partial \theta_j}$h(x)  I've been looking at this for a while and I can't see where this minus sign is coming from...  Thanks for your help! I would like to find a way to construct uncountably many non-isomorphic linear (total) orderings of natural numbers (as stated in the title).  I've already constructed two non-isomorphic total orderings. They are $$ 1 &lt; 2 &lt; 3 &lt;\ldots\\ 1 &gt; 2 &gt; 3 &gt;\ldots $$ where "$&lt;$" and "$&gt;$" are  strict total ordering relations.  Thanks in advance for your help. Floquet and Bloch's theorems : connection? It is often stated that  and  are equivalent, even the Bloch's theorem is often referred as Floquet-Bloch theorem.  However, it seems quite confusing to me since the former involves a second order differential equation (Schroedinger equation with a periodic potential) while the latter is defined for a first order one.  Can someone clarify this to me? Also it would be nice if I can get references that connect the two. As my client software uses lat/lon coordinates when communicating with my (spherical mercator) postgis database i decided to ST_Transform every geometry to WGS-84.  However i noticed that ST_Distance for WGS-84 returns units as degrees (i need meters). So i decided to use ST_DistanceSpheroid(geom1, geom2, 'SPHEROID["WGS 84",6378137,298.257223563]') but this method seems to be extremely slow.  Therefor i switched back to using spherical mercator again and transforming my input and output to and from wgs-84 as that performs a lot better.  Am i using the correct method or is this a known issue? Can a Tourist from a VWP country carry (Rent/ Borrow) a gun in say Florida Looking to find out if it is legal to borrow or rent a gun from an individual(s) or company to use to either visit the various gun ranges or wildlife hunting in Florida.  I have a shotgun licence in the UK for hunting etc... but looking to do something similar in Florida without falling foul of any gun carrying laws in transit to any gun range or hunting area?  I know various friends in the US that would lend the guns while there but are they required to be with me while attending any event? Basically not looking to be tethered to any third party... What's the meaning of the transpose? Proof of a formula involving Euler's totient function: $\varphi (mn) = \varphi (m) \varphi (n) \cdot \frac{d}{\varphi (d)}$ Why non-measurable sets exist? What Is the reason behind the fact that $\Bbb R$ is not a complete measure space? Is it only due to the cardinality of  $\Bbb R$? Or other structures on  $\Bbb R$ also play a role? Can one make every subset of  $\Bbb R$ trivially measurable by assigning them to a number of a complete ordered field of the cardinality $\aleph_2$ ? Do not hide VLQ flag option from users who already flagged and may wish to retract For every vector space $V$ does there exist a linear functional $f$ ( a linear map from $V$ to $F$ the underlying field ) such that for some $ \vec v \in V$ , $f(\vec v) \ne 0$ ? If it does exist , can we prove the existence without the "axiom of choice " ? Is the existence equivalent to axiom of choice ? How do comment @replies work? How do the comment replies (aka &quot;pinging users&quot;) work?  Who can I send an @reply to? How do I respond to a specific user when entering my comment? Will they be notified? What do people mean when they talk about &quot;pinging&quot; another user?  Related: Fine, the 's math  did in the old pop-up. That makes sense. But this is just silly. Why do I need to be notified that a post I downvoted got deleted?    (The title links next to the red -1s were removed from the screenshot by me. They're present in the real pop-up.)  So I can break out a bottle of the '82 Rothschild? It's especially pointless because there's  that caused the change.  Please don't display the Rep Signal when the change is only due to someone else's deleted posts. Bluetooth Broadcom 43142 isn't working When and where does Attack on Titan take place? Is the setting of "Attack on Titan" (Shingeki no kyojin) supposed to be Earth in the distant future and Titans suddenly appeared out of nowhere and devolved society to medieval level of technology? Or is this just a completely fictional setting? A clock in freefall Time dilation  using Schwarzschild metric for a non rotating spherical body is: $$t_0=t_f\sqrt{1-\frac{2GM}{rc^2}}$$  For such a non rotating spherical body, what would the time dilation of a clock in vacuum free-falling from infinity be?  (If the answer is non-trivial; a high level outline of the calculation would suffice / be appreciated)  Edit: I am currently working on an iOS app that is trying to model the mechanism underpinning relativity.  So, far the mechanism that I have created is shockingly simple and shockingly good at conforming to Relativity.  However, I am trying to break it.  I am trying to find any possible areas where the two may diverge.  I have noted that using my model a clock in freefall will experience no time dilation, i.e. $t_0=t_f$ and I want to make sure Relativity agrees.  I have noted the gravitational component of time dilation above.  Since my clock is moving one might also expect a kinematic time dilation.  I can calculate the velocity of my clock: $$E_k=\frac{1}{2}mv^2$$ $$E_p=\frac{-GMm}{r}$$ $$v=\sqrt{\frac{2GM}{r}}$$ Plugging this velocity into the kinematic time dilation equation: $$\Delta t'=\frac{\Delta t}{\sqrt{1-\frac{v^2}{c^2}}}$$ $$\Delta t'=\frac{\Delta t}{\sqrt{1-\frac{2GM}{rc^2}}}$$  At this point one might make the observation that the kinematic dilation is the inverse of the gravitational dilation and therefore conclude that: $$t_0=t_f$$ Using HTML5/Canvas/JavaScript to take in-browser screenshots Calculating grid convergence (True North to Grid North) I would like to know how to calculate the grid convergence angle between True North and Grid North for UTM maps. I am using ArcGIS 10.0 (ArcView licence). and have used the  tool from the Cartography toolbox. However, I would like to know how to calculate this angle myself (using Excel) to compare against the ArcGIS result?