newenvironment : synonym for an existing environment
newenvironment: error with \begin{align} and \end{align}
What is the difference between test set and validation set? I found this confusing when I use the neural network toolbox in Matlab. It divided the raw data set into three parts:   training set validation set test set   I notice in many training or learning algorithm, the data is often divided into 2 parts, the training set and the test set.  My questions are:   what is the difference between validation set and test set?  Is the validation set really specific to neural network? Or it is optional. To go further, is there a difference between validation and testing in context of machine learning? Why do we need both using namespace and include directives in C++ programs?  For example,   #include &lt;iostream&gt;  using namespace std;  int main() {  cout &lt;&lt; "Hello world"; }   Why is it not enough to just have #include &lt;iostream&gt; or just have using namespace std and get rid of the other?  (I am thinking of an analogy with Java, where import java.net.* will import everything from java.net, you don't need to do anything else.) How to convert an instance of std::string to lower case Distance Between Two Points in Matlab I have a string User name (sales) and I want to extract the text between the brackets, how would I do this?   I suspect sub-string but I can't work out how to read until the closing bracket, the length of text will vary. Can Jupiter be ignited? Our solar system itself contains two candidate "Earths"  One is Jupiter's moon Europa and another is Saturn's moon Titan. Both of them have the problem of having at low temperature as Sun's heat cannot reach them.    Jupiter is made up mostly of Hydrogen so is our Sun. Can we ignite Jupiter so that it will produce enough heat to warm these two earth like planets/satellites? What can be consequences of any of such attempt? The escape velocity of earth is roughly $11 kms^{-1}$. However, what if a long ladder was built extending out of Earth's atmosphere and considerably more. Then if something was to climb up at much less than the escape velocity, what would happen when it reached the end?  And what if the object that climbed the "ladder" then fired some kind of thruster/rocket and was going fast enough so that it orbited the Earth. It would mean less energy required to get into orbit? Fire (at, on, in, to) target How to correctly choose the preposition in "fire (at, on, in, to) target"? Why commutator subgroup is normal to G? If $G$ is a group and $G'$ is generated by $\{xyx^{-1}y^{-1}|x,y\in G\}$, then $G'\trianglelefteq G$ and  $G/G'$ is Abelian.  At first, I thought this is easy because I thought $g[x,y]g^{-1}=[gxg^{-1},gyg^{-1}]$. But it was a mistake. I could not prove that it is also subgroup of G and $G/G'$ is abelian. I need help. Ignored users still appear in the 'other rooms you're in' message preview Well it might not be a huge issue to some (I suppose it depends on how you use the chat system) but when I "Ignore this user everywhere", their messages still appear on the sidebar for the 'other rooms you're in' if they say something. Albeit I can ignore this feature and the text within it, I just find it odd that I can still see it.   This is only a nuisance when you truly are annoyed by a user and ignoring them in the chat was the best possible alternative to leaving the room or starting an argument (no references here, but any long time chat user has been annoyed by some help vampire at one point in time or another and would just prefer to ignore them for good).   If you have no clue to the sidebar or preview I'm talking about: this is for you,    I have chosen to Ignore this user everywhere (Neal) and then switched to a new room, yet that users response appears in my 'preview' for the 'other rooms you're in' if he is also talking in them.  Note: My ignore of Neal was mostly due to jest, this in no way is to reflect on Neal but the chat feature (I hate to ever single anyone out here). Did anyone in the Star Wars universe wear effective armour? The Storm Troopers are the main case here, they get killed easily by blasters and even the Ewok arrows go straight through their 'armour'.   The AT-ST and AT-AT use armour to repel blasters of different strengths so they don't pass through all materials. I understand though that the armour used on these is likely much heavier.   From the prequel trilogy we also have the , which have a shield when not moving. Does anyone other than these droids use this technology?   You may use any of the Scrapped EU, Current EU and the normal U to answer. Display current layout (language code/country flag) in keyboard indicator Just upgraded from 10.04 to 10.10, and the keyboard indicator applet no longer displays the two-letter country code for the active layout.  This is terrible. Is this the default behaviour? Anyone using two layouts can't tell which language they're in.  I can't seem to find the setting for this, it used to be in the preferences for keyboard layout.  Update 1: In case this wasn't obvious - I have two keyboard layouts - English and Hebrew. I just upgraded form 10.04, where the country code (USA/IL) was displayed, overlaid on the flag.  Now all I get is a vague keyboard icon, and can't find the settings for this.  Update 2: this seems to be a , and is now back in Maverick Dissolve (merge) polygons QGIS based on attribute values only when are adjacent Remove particularly tricky items from context menu I've found various sources of info about removing these annoying things which I never use... but I haven't succeeded in getting rid of the following.    (Avira-related:) - Scan selected files with Avira  (I believe all this is M$ crapware... I presume it's all been lovingly crafted so they're all impossible to remove. You never know, though: some super-uber-uber-geek might just have found a way) - Restore previous versions  - Cut - Copy - Delete  - Rename I am using ArcMap 10.2 and want to represent a layer in a rotated dataframe with chart (graph) symbology. The problem is that the charts do not rotate with the dataframe:     I thought I could convert to graphics and rotate each chart individually, but   that is very tedious I don't find an option to convert a layer to graphics, works for the legend but not for the actual layer symbology How do you persuade an organization to value UX? UX is such an underrated field in a lot of industries. I wonder how companies consider employing UX designers and even heavily valuing their suggestions. Some big companies happen to see the light and invest in UX, and that keeps them on top of others. However, UX people rarely make it to the top management. In Don Norman's talk (  ), out of so many UX people (I don't know exactly), only two were vice presidents. I assume that there are even less influential UX designers in developing countries, and that's what makes it even harder for people like me. In the same talk, Don Norman suggested that UX designers should approach their executives like marketing people, showing how investing in something will affect profit. Perhaps, it's the best thing to do but it has to be mastered for it to be executed successfully.   I'm a fresh grad and am looking for a job. I think, working for a company with a more conventional job description would be the way to go. When I'm already influential enough, I'll go up to the executives and show them how UX will improve sales (in whatever industry it is. I just want to do UX)  Do you do UX as consultants or are you employed? How do you persuade companies to invest in UX? Are you lucky enough to be employed by people who you didn't have to persuade to value UX? Orbiting a specific point - Orbiting Camera Could someone explain the muon $g-2$ experiment problem? How to view the system console message after Blender crashes? I am testing a script in Blender game engine. I can view the helpful message on the external system console when the script throws exception. Sometimes the bugs of the script cause the Blender to crash and close the console immediately.    Is there any way to view the message after the Blender crashes? How to write the message to a text file for later viewing? Any suggestion? One-dimensional vector space and it's subspaces