I have a network of roads and I would like to obtain a graph made by edges, each of them delimited by a origin node and a end node, such as the picture shows.    I would like to obtain a table made of rows like this      "edge_id, origin_node_id, end_node_id, origin_node_X, origin_node_Y, end_node_X, end_node_Y"    for example, for the a12 edge: "a12, 48.1234, 50.0000, 48.1335, 49.1111", where the origin node 1 coordinates are (48.1234,50.0000) and the end node 2 coordinates are (48.1335,49.1111).  I used the field calculator with these expressions:     x_at(0),y_at(0),x_at(1),y_at(1)    to get "origin_node_X,origin_node_Y,end_node_X,end_node_Y".  Now I am searching for a way to obtain the id of nodes which obviously are in another layer.   So I think that I could need a field calculator expression or python code to relate nodes' layer with edges' layer. I think that "get_feature" could be useful but at the moment I did not find the right way to use it. Another option is to make a text output file with python.
Does anyone have a simple work-flow for drawing cross sections of earth features in QGIS?   My thing is that QGIS is being used to present the plan view, but we have a little interest in some elevations as well. All the data is one set and is simply an elevation value in the attribute table, I don't want to have to move all that to CAD.  One logical workaround is to present the z value as the y.  I am a dunce in paper space in CAD, and would be more comfortable with the QGIS Composer.
The problem is to prove that every Hilbert space has a orthonormal basis. We are given Zorn's Lemma, which is taken as an axiom of set theory:  Lemma If X is a nonempty  with the property that every  of X has an upper bound in X, then X has a maximal element.   Given a orthonormal set $E$ in a Hilbert space $H$, it is apparently possible to show that $H$ has an orthonormal basis containing $E$.   I tried to reason as follows: Suppose $E$ is a finite set of $n$ elements. Then one can number the elements of $E$ to create a totally ordered set of orthonormal elements. Then the span $&lt;E&gt;$ can be identified with $R^n$, where each element $v = v_1 e_1 + v_2 e_2 + ... + v_n e_n$ is identified with the vector $(v_1, v_2, ..., v_n)$. On $R^n$ we have a total order, namely the "lexigraphical order" $(x_1,x_2,...,x_n) \leq (y_1,y_2,...,y_n)$ if $x_1 &lt; y_1$ or if $x_1 = y_1$ and $x_2 &lt; y_2$ or if $x_1 = y_1$, $x_2 = y_2$ and $x_3 &lt; y_3$ and so on. Hence $E$ is a totally ordered subset of $H$ and $H$ is a partially ordered set. However, this set doesn't seem to have an upper bound. The set $E$ does have an upper bound. If we define a total order on $E$ only, then X is a partially ordered set satisfying the criteria so X has a maximal element?   This is as far as I got, and I am not sure the entire argument is correct. I don't see how what kind of maximal element I am seeking, since the orthonormal basis of a Hilbert space can have countably infinity number of elements. How do I check if a number is a palindrome?  Any language. Any algorithm. (except the algorithm of making the number a string and then reversing the string). What finite groups always have a square root for each element? If $G$ is an odd cyclic group of order $n$, then each element $g$ of $G$ has another element $h$ such that $h^2=g$. This is because $2 x = y \mod n$ is solvable for $x$. (Note this is not the same as solving $x^2=y \mod n$.)  What other finite groups have this property? How can I do a full shutdown of windows 10 without logging in? What do solid/striped lines on a wire indicate? What do solid or dashed lines on a wire indicate?  Is there a difference between the solid and dashed indicators? How to prove the property of the Lemoine point of a triangle? From Wolfram , I know there is a Lemoine point of triangle, also called symmedian point, the sum of squared distances of this point to all the three sides is algebraically minimum.    How to prove such a property? How do I remove Ubuntu's password requirement? Is there a difference between "think of something" and "think about something"? I've also met "have heard of/about something". Pending suggested edit message bug I just tried to edit a post on Stack Overflow but when I pressed the 'edit' button it showed me this message on a white page.    I know what the message means but I don't think it is supposed to show up in a white page. So, is this a bug or is it something else? How to automaticaly enter sudo's grace period upon login P.d.f of the absolute value of a normally distributed variable I came across this question as an exercise, had a brief idea, but didn't know how to proceed.     Let $X \sim N(0, 1)$. What is the p.d.f of $|X|$ ?   I know the final p.d.f looks just like the right half of the original pdf, but extended vertically for a factor of 2.  Could someone please show mathematically what the p.d.f of variable |X| is going to be, and explain briefly? Thank you. Is circular reasoning always a fallacy? Deductible expenses paid with credit card: In which tax year would they fall? If I paid my business expenses with a credit card during the month of December, which year can I deduct them from my taxes? 2011 (when the purchase was made) or 2012 (when I paid off the credit card)?  IRS pub reference greatly appreciated If $p$ is a prime and $p \mid ab$, then $p \mid a$ or $p \mid b$. The proof is already given in the textbook but I tried other way around.   Proof by contradiction: Let's assume that $p$ doesn't divide $a$ and $p$ doesn't divide $b$, but $p$ divides $ab$. So $\gcd(p,a)=1$ and $\gcd(p,b)=1$. Given that we can construct linear combinations   $sp+ta=1$ together with $up+wb=1$. Multiplying the left and the right sides of the equations we get  $spup+spwb+taup+tawb=1$ or $p(sup+swb+tau)+ab(tw)=1 \implies \gcd(p,ab)=1$. This is a contradiction.   Is it rigorous and sound proof? When will my device get the Android 4.2 update (Jelly Bean)? How do you explain cubic growth of a function When reading scientific papers I have seen people explain the growth of a variable linearly, exponentially. However how would one say for a variable which grows in quadratic fashion, or cubic?  I don't remember reading something like: "y grows cubically with x"  Can I say, y grows cubically with x?  What would be the proper way to explain cubic or quadratic growth of a variable as a function of another one?  How would you explain the given lines: Which is correct: "has died" or "died"? To me, using Present Perfect form means the event can occur again. So, saying      someone has died   may not be grammatically correct.  Also, I noticed (it might be just coincidence):     passed away   is used more often than     has passed away   Is using Present Perfect correct here? How to get the last argument to a /bin/sh function What's a better way to implement print_last_arg?  #!/bin/sh  print_last_arg () {     eval "echo \${$#}"  # this hurts }  print_last_arg foo bar baz # baz   (If this were, say, #!/usr/bin/zsh instead of #!/bin/sh I'd know what to do.  My problem is finding a reasonable way to implement this for #!/bin/sh.)  EDIT: The above is only a silly example.  My goal is not to print the last argument, but rather to have a way to refer to the last argument within a shell function.    EDIT2: I apologize for such an unclearly worded question.  I hope to get it right this time.  If this were /bin/zsh instead of /bin/sh, I could write something like this  #!/bin/zsh  print_last_arg () {     local last_arg=$argv[$#]     echo $last_arg }   The expression $argv[$#] is an example of what I described in my first EDIT as a way to refer to the last argument within a shell function.  Therefore, I really should have written my original example like this:  print_last_arg () {     local last_arg=$(eval "echo \${$#}")   # but this hurts even more     echo $last_arg }   ...to make it clear that what I'm after is a less awful thing to put to the right of the assignment.  Note, however, that in all the examples, the last argument is accessed non-destructively.  IOW, the accessing of the last argument leaves the positional arguments as a whole unaffected. .NET - How can you split a "caps" delimited string into an array? How do I go from this string: "ThisIsMyCapsDelimitedString"  ...to this string: "This Is My Caps Delimited String"  Fewest lines of code in VB.net is preferred but C# is also welcome.  Cheers! Conjugate subgroup strictly contained in the initial subgroup?