I'm trying to collect input on a revision to my town's mainstreet.  Is it possible to create a map where a visitor can click a point, and answer a few questions about that point?  (OK I was told that this question is too broad, so I am going to try to refine it)    Essentially, I want to be able to embed this map on the city's website, then invite community members to visit it and place markers at points on Main Street that they either like/dislike.  Ideally they would be able to drag a red or a green marker onto the map, which prompts one or two questions about the site, then move on.    I expect this could be done many different ways, but I really don't even know where to start looking for a solution.
I want to start working on a web map at work to map some of our statistics by city.    I have an idea, but I'm not exactly sure where to start.   Are there any definitive resources that provide step by step guidance on how to do this?
I am using postgreSQL, postGIS and pgrouting. Now I am really confused on how am I going to find the shortest path between multiple points.   I know how to find it between two points through dijkstra but I am confused how to accomplish the same result with more than two points.   I have done some research and found this:    But still I did not understand if its the right way and how to install it. How to understand degrees of freedom? From , there are three interpretations of the degrees of freedom of a statistic:     In statistics, the number of degrees of freedom is the number of   values in the final calculation of a statistic that are free to vary.      Estimates of statistical parameters can be based upon different   amounts of information or data. The number of independent pieces of   information that go into the estimate of a parameter is called the   degrees of freedom (df). In general, the degrees of freedom of an   estimate of a parameter is equal to the number of independent scores   that go into the estimate minus the number of parameters used as   intermediate steps in the estimation of the parameter itself (which,   in sample variance, is one, since the sample mean is the only   intermediate step).      Mathematically, degrees of freedom is the dimension of the domain of a   random vector, or essentially the number of 'free' components: how   many components need to be known before the vector is fully   determined.   The bold words are what I don't quite understand. If possible, some mathematical formulations will help clarify the concept.  Also do the three interpretations agree with each other? I have just reinstalled Apache and PHP5 but when I visit my doc root it just downloads a "download" file. And when I try documentroot/index.php it just downloads the PHP file.  I have PHP installed but Apache doesn't seem to want to execute it. People suggested adding a 'Load Module' line to my httpd.conf but I don't have that file. Identify the plane defined by $|z-2i| = 2|z+3|$ I tried:  $$|z-2i| = 2|z+3| \Leftrightarrow \\ |x+yi-2i|=2|x+yi+2|\Leftrightarrow \\ \sqrt{x^2+(y-2)^2}=\sqrt{4((x+2)^2+y^2)} \Leftrightarrow \\ \sqrt{x^2+y^2-4y+4} = \sqrt{4x^2+24x+36+4y^2} \Leftrightarrow \\ x^2+y^2-4y+4 = 4x^2+24x+36+4y^2 \Leftrightarrow \\ y^2-4y-4y^2=4x^2+24x+36+x^2 \Leftrightarrow \\ -3y^2-4y=5x^2+24x+26 \Leftrightarrow \\ ???$$  What do I do next? Relationship between balloon size and pressure I see numerous websites talking about how a small balloon is at higher pressure than a big balloon. This is a fun counter-intuitive factoid... unless it isn't a fact at all.  Young-Laplace gives  $$T = \Delta p \frac R2 $$  Which means that for a given tension, increasing the radius does decrease the pressure. But why would the tension be constant? A latex balloon is like a 2D spring, right? So the tension in a inflated spherical balloon should be proportional to the surface area, correct?  $$T \propto R^2 $$  But this gives  $$\Delta p \propto R$$  Which means the bigger the balloon, the higher the internal pressure. Which, again, would be the normal intuition - but it would burst the bubble of some simplified explanations. (har har) Question about "surely" and "certainly" Today I saw a sentence:  She surely can do it.  What does that mean? How does it differ from:  She certainly can do it. Surely she can do it.  This slight difference in meaning of those sentences I am not able to notice. Could you please help me? Thanks in advance! Question mark and colon in JavaScript ID a book about a mirror world and 4th dimension I read a book about 10-15 years ago about a boy and a girl who find a mirror. What made the mirror special was, they were able to enter the reflection and be a part of the reverse image world. They end up going to school and when asked to write something on the board, it ends up being backwards, but to them looks normal.  Later, the two end up in a world with 4 dimensions. With the added dimension they can't see as they normally could. If one moved a certain way the other would see their insides. Eventually a native of that dimension made some type of device that lets them see regularly.  Other than that my memory is blank. If I remember anything else I will be sure to edit it in. Every finitely generated algebra over a field is a Jacobson ring Knowing that the polynomial ring in $n$ variables over a field $k$ is a Jacobson ring, how can we prove from it that every finitely generated $k$-algebra is a Jacobson ring?   EDIT: We define a ring to be Jacobson if every prime ideal is an intersection of maximal ideals. Euclidean geometry in non-inertial frame Work done in adiabatic process Origin of the dot and cross product? Most questions usually just relate to what these can be used for, that's fairly obvious to me since I've been programming 3D games/simulations for a while, but I've never really understood the inner workings of them... I could get the cross product equation as a determinant of a carefully-constructed matrix,   but what I want to ask is... How did the dot and cross product come to be? When were they "invented"? Some detailed proofs? Did someone say: "Hey, wouldn't it be nice if we could construct a way to calculate a vector that is perpendicular to two given operands?"  Basically, how/why do they work?  I would appreciate explanations, links to other explanations, other web resources... I've been searching the Internet lately for explanations, but most of them are on how to use it and nothing that really gives substance to it. Need help to install persistent Ubuntu on USB drive Possible Duplicate:          I am a new user of Ubuntu. I would like to install a persistent Ubuntu 11.04 to my USB stick, and it should be able to work as a guest OS running on Windows so that I can boot it on other computers other than the one which I used for the installation. I have used several creators such as unetbootin, however from my understanding it can only create Live Linux which I am unable to save my configurations and files. If it's possible I would like to bypass the BIOS, that is to say that I can just load from the virtual machine without having to restart the computer. Thanks in advance!    Thanks for all the replies! Hi Mike, I am able to create a virtual machine and run it from my USB drive using a portable virtualbox. How do I go about from there, do I have to proceed with the installation? Could you elaborate more on the steps for the installation? Thanks again! Suppose we have a random variable $X \sim f(x|\theta)$. If $\theta_0$ were the true parameter, the the likelihood function should be maximized and the derivative equal to zero. This is the basic principle behind the maximum likelihood estimator.   As I understand it, Fisher information is defined as   $$I(\theta) = \Bbb E \Bigg[\left(\frac{\partial}{\partial \theta}f(X|\theta)\right)^2\Bigg ]$$  Thus, if $\theta_0$ is the true parameter, $I(\theta) = 0$. But if it $\theta_0$ is not the true parameter, then we will have a larger amount of Fisher information.   my questions    Does Fisher information measure the "error" of a given MLE? In other words, doesn't the existence of positive Fisher information imply my MLE can't be ideal?  How does this definition of "information" differ from that used by Shannon? Why do we call it information? So, the question pretty much says it all. I'm on Snow Leopard, and I do a lot of web development, particularly in Rails 3 which makes heavy use of the console.  I've seen some notable bloggers etc. mention Zsh as their preference over Bash, but I don't know what difference it would make.  Could anyone give me a good comparison of what difference there is and what might make one prefer one option or the other? Are you allowed to stack Divine Smite and Eldritch Smite on the same attack? Turning off "Update page numbers only" in Word When I update the fields document-wide (Ctrl + A, then F9) in a Word document that has a table of contents, a dialog appears asking if I want to update page numbers only, or update the entire table. I never want to update page numbers only if the document headings have changed, nor will I ever.  (Apparently this is given as an option in case someone has manually changed an automatically generated ToC, which is almost always a really bad idea.)   Unfortunately, "Update page numbers only" is the default selection in the dialog, which means that I have to select the other option every time. I update the fields all the time when I'm working in a document that has figures and cross-references, so this is an annoying extra step I'd really like to get rid of.   Is there any way to tell Word to stop asking me this stupid unnecessary question? How to typeset asymmetrical confidence level limits / uncertainties? Below is an example of an asymmetrical limit (or uncertainty)  How can I typeset this in a \LaTeX equation? Such pair of numbers should be vertically stacked while being vertically center-aligned with rest of the equation. Solution $X^{+Y}_{-Z}$ What's the difference between adjusting highlights and shadows in the basic panel and in the tone curve in the Develop Module of Lightroom? I wanted to reduce some highlights in a photo and found that there were two possible ways of doing so: one from the basic panel and another from the tone curve. when I reduce the highlights in one pane the value on the other is unchanged. Are both of them the same thing? Which would be better? How to record how much time user has spent on my node? I want to record the time a user has spent on my particular node so I could show a pop up to the user to register once the user has read 3 article. But the user must have spent at least 30 seconds on each node.   There is the  module available, but I wonder if I can merge it with another (custom) module I have created (which records the number of nodes user have visited)?