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• How to represent a list of points in R

  - by Guido

  I am working with a large list of points (each point has three dimensions x,y,z). I am pretty new with R, so I would like to know what is the best way to represent that kind of information. As far as I know, an array allows me to represent any multidimensional data, so currently I am using: > points<-array( c(1,2,0,1,3,0,2,4,0,2,5,0,2,7,0,3,8,0), dim=c(3,6) ) > points [,1] [,2] [,3] [,4] [,5] [,6] [1,] 1 1 2 2 2 3 -- x dim [2,] 2 3 4 5 7 8 -- y dim [3,] 0 0 0 0 0 0 -- z dim The aim is to perform some computations to calculate the euclidean distance between two sets of points (any hint in this sense would also be highly appreciated)

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• 3D points to quaternions

  - by Hubrus

  For the simplicity, we'll consider two 3D points, that moves one relatively to other, in time. Let's say: at moment t0, we have P1(0,0,0) and P2(0,2,0) at moment t1, P1 is still (0,0,0) but P2 changed to (0,2,2). From what I've understood reading about quaternions, is that, at moment t0, Q1 (representing P1) and Q2 (representing P2) will be both (0, 0, 0, 0). But at the moment t1, Q2 will become something else (w, x, y, z). How do I calculate the Q2 at t1 moment? I've googled a lot on this subject, but I was able to find only rotation between quaternions. I will appreciate any guidance. Thanks!

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• In SQL, how can I count the number of values in a column and then pivot it so the column becomes the

  - by Josh Yeager

  I have a survey database with one column for each question and one row for each person who responds. Each question is answered with a value from 1 to 3. Id Quality? Speed? -- ------- ----- 1 3 1 2 2 1 3 2 3 4 3 2 Now, I need to display the results as one row per question, with a column for each response number, and the value in each column being the number of responses that used that answer. Finally, I need to calculate the total score, which is the number of 1's plus two times the number of 2's plus three times the number of threes. Question 1 2 3 Total -------- -- -- -- ----- Quality? 0 2 2 10 Speed? 2 1 1 7 Is there a way to do this in set-based SQL? I know how to do it using loops in C# or cursors in SQL, but I'm trying to make it work in a reporting tool that doesn't support cursors.

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• Add Expansion Button to Stackpanel

  - by scientist

  I'd like to add Elements to a StackPanel (or Listbox / Listview if it would make that easier) and automatically add a Button (like "...") to indicate that there are more children than there is space for. Consider a calendar that has appointment items in each day. If there are more appointments than as much as can be displayed a button is displayed to go to a detailed view for that day. Can this be done automatically, or how do I calculate the positions of the stackpanel and its items. It's for windows store development in c#. Thanks in advance.

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• How to get the number of loop when using an iterator, in C++?

  - by pollux

  Dear reader, I'm working on a aplication where I draw a couple of images, like this: void TimeSlice::draw(float fX, float fY) { list<TimeSliceLevel*>::iterator it = levels.begin(); float level_x = x; float level_y = y; while(it != levels.end()) { (*it)->draw(level_x,level_y); level_y += (*it)->height; ++it; } } Though this is a bit incorrect. I need to position the TimeSliceLevel* on a X.. When I've got a for(int i = 0; i < slices.size(); ++i) loop, I can use x = i * width. Though I'm using an iterator as I've been told many times that's good programming : and I'm wondering if the iterator has a "index" number of something which I can use to calculate the new X position? (So it's more a question about using iterators) Kind regards, Pollux

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• Sending a large file over network continuously

  - by David Parunakian

  Hello, We need to write software that would continuously (i.e. new data is sent as it becomes available) send very large files (several Tb) to several destinations simultaneously. Some destinations have a dedicated fiber connection to the source, while some do not. Several questions arise: We plan to use TCP sockets for this task. What failover procedure would you recommend in order to handle network outages and dropped connections? What should happen upon upload completion: should the server close the socket? If so, then is it a good design decision to have another daemon provide file checksums on another port? Could you recommend a method to handle corrupted files, aside from downloading them again? Perhaps I could break them into 10Mb chunks and calculate checksums for each chunk separately? Thanks.

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• How can I determine what text on a webpage will render the largest?

  - by TMG

  I'd like to write a function (ideally in PHP) where I can input a url and return a string corresponding to the hypertext from that webpage which would render the largest in a browser (any standard browser is fine). Getting the webpage and tokenizing things with DOM is pretty straightforward, but what's the best way to calculate ultimate size of the rendered text tokens - how do you account for CSS that includes px, em, % etc. for different font sizes. Anyone done something like this before I go and re-invent the wheel? Thanks in advance.

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• How to use the variable declared in one class in another class in Obj C.

  - by srikanth rongali

  I have a NSDate *date1 in class1 implementation file(I initialized it as Global variable). I have NSDate *date2 in class 2 implementation file (initialized it as Global variable). I need to calculate the NSTimeInterval between the two dates in class 2. But I could not do it. I could not access date1 in this class. It is giving error as (date2 undeclared). Please give me help in how to call other class variables in this class. Thank you.

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• How to move file pointer to a particular location using fseek()?

  - by Noge

  My intention is to read every elements in the 2nd column into a buffer[] from the following .txt file: 9992891234 09.920 15.771 11.909 9992345971 07.892 12.234 09.234 9992348971 64.567 70.456 50.987 9992348231 89.234 85.890 58.982 I have know of a way to do it by using fscanf(): for (int i=0;i<4;i++) { fscanf(pFile, "%lld", &junk); fscanf(pFile, "%f", &buffer[i]); fscanf(pFile, "%f", &junk); fscanf(pFile, "%f", &junk); } However, since I'm doing parallel programing which requires me to use different Windows Threads to read different columns, so I'll need to read the elements in the 2nd column directly using fseek(). The question here is, what should I put in the 2nd argument in fseek() in the code below to move my file pointer to read the 2nd element of the 2nd line? fscanf(pFile, "%llf", &junk);//<------this is used to skip the 1st data for (int i=0;i<4;i++) { fscanf(pFile, "%f", &buffer[i]); fseek ( pFile , ??, SEEK_CUR );//<----how do I calculate this offset? }

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• Store data in Ruby on Rails without Database

  - by snowmaninthesun

  I have a few data values that I need to store on my rails app and wanted to know if there are any alternatives to creating a database table just to do this simple task. Background: I'm writing some analytics and dashboard tools for my ruby on rails app and i'm hoping to speed up the dashboard by caching results that will never change. Right now I pull all users for the last 30 days, and re arange them so I can see the number of new users per day. It works great but takes quite a long time, in reality I should only need to calculate the most recent day and just store the rest of the array somewhere else. Where is the best way to store this array? Creating a database table seems a bit overkill, and i'm not sure that global variables are the correct answer. Is there a best practice for persisting data like this? If anyone has done anything like this before let me know what you did and how it turned out.

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• im writing this code so the user would enter his/her name and followed by his/her marks to get the a

  - by WM

  What if the user wanted to enter his/her grades in the following way: Will 23, 34, 45, 45 how would i get rid of the commas public class StudentAverage { public static void main(String[] args) { int markSum = 0; double average = 0; Scanner input1 = new Scanner(System.in); System.out.print("Enter student record : "); String name = input1.next(); Scanner input2 = new Scanner(input1.nextLine()); int countTotal = 0; while (input2.hasNextInt()) { countTotal++; markSum += input2.nextInt(); } average = markSum / countTotal; // to calculate the total average System.out.print( name + " " + average ); } }

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• Strange calculation problem in C multiply by 1.2 fails

  - by DoomStone

  I have this c code, where i need to calculate a dobule from a long. double result; long t2_value; t2_value = 72; result = t2_value * 1.2; Now this code crashes at "result = t2_value * 1.2;" only with the error "Vector 0000000006". Here is the strange thing, if i replace result = t2_value * 1.2; with result = 72 * 1.2; evything works just as it should, i have tryed type casting t2_value as an double result = ((double)t2_value * 1.2); or making it an int istead of a long, but nothing helps.

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• Doesn't Matlab optimize the following?

  - by kloop

  I have a very long vector 1xr v, and a very long vector w 1xs, and a matrix A rxs, which is sparse (but very big in dimensions). I was expecting the following to be optimized by Matlab so I won't run into trouble with memory: A./(v'*w) but it seems like Matlab is actually trying to generate the full v'*w matrix, because I am running into Out of memory issue. Is there a way to overcome this? Note that there is no need to calculate all v'*w because many values of A are 0. EDIT: If that were possible, one way to do it would be to do A(find(A)) ./ (v'*w)(find(A)); but you can't select a subset of a matrix (v'*w in this case) without first calculating it and putting it in a variable.

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• How to read changed values with native query during one transaction? (Spring and JPA)

  - by knarf1983

  We have container transaction with Spring and JPA (Hibernate). I need to make an update on a table to "flag" some rows via native statements. Then we insert some rows via EntityManager from JPATemplate to this table. After that, we need to calculate changes in the table via native statement (with Oracle's union and minus, complex groups...) I see that changes from step 1 and 2 are not commited and thats why the statement from 3 fails. I already tried with transaction propagation REQUIRES_NEW, EntityManager.flush... Didn't work. 1) update SOMETABLE acolumn = somevalue (native) 2) persist some values into SOMETABLE (via entity manager) 3) select values from SOMETABLE Is there a possibility to read the changes from step 1 and 2 in step 3?

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• PHP: Star rating system concept?

  - by Prashant

  I am using PHP/MYSQL/JQUERY. I have a site which have news section. On news details page, I want to add star rating system which will allow user to rate the news story. I am using this jquery rating system http://www.fyneworks.com/jquery/star-rating/ Now, I am not getting what will be the database structure and then what I need to code in PHP. I need what logic will be applied for this, like if 1000 people voted for the article, some given rating as 2 or 3 or1 or 5. Then Where I should be storing (db structure) this all and what I'll calculate (in php code). If someone has any article which shows this concept please provide. Please help, to understand the logic and concept of this. Thanks!

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• Math Problem With Percentages

  - by TheDarkIn1978

  i'm terrible at math. trust me, you math experts will see why after reading my question. i have an object that is 300px in height. i need to calculate the percentage of that height where 90% = 300px (or the full height), 45% = 150px, 0% = 0px. so essentially, if i ask for 45% of the object's height, it will return 150px, or if i ask for 32% of the object's height, it will return __? i believe this is really basic math, so i apologize in advance.

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• MATLAB help required function root

  - by programmeur

  Dear All, I have made an program, function bisection; x1=input('enter the first value=') x2=input('enter the second value=') %f3=[]; for x=1:20 %x=1; x3=(x1+x2)/2; while x3-x1 >= 0.001 f3(x)=x3^3 + x3^2 - 3*x3 - 3; f1(x)=x1^3 + x1^2 - 3*x1 - 3; if ((f3(x)*f1(x)) < 0) x2=x3; else x1=x3; end break end format long f3' disp('The root is found to be ='); x3 end . . . . . program calculate function of interval (x1, x2) given by user, my program compile and execute but little stupid repetition until for loop complete, i want to stop further printing loop when desired value is achieved with while condition is used.

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• php script to generate checksum from md5

  - by sumit

  In order to calculate the checksum i need following things. these parameters are concatenated in a constant (no spaces) string made up of the values of the following parameters in the exact order listed below: o Secret Key o Merchant id o Currency o Total amount o Item list (item_name_1, Item_amount_1, item_quantity_1 to item_name_N, Item_amount_N, item_quantity_N) o Timestamp e.g In that case the string befor hash will be: pLAZdfhdfdNh57583USD69.99Tier2 item69.9912010-06-14.14:34:33 And using the MD5 hash function the result is: ghvsaf764t3w784tbjkegbjhdbgf i want to know how can i create a php script that will call md5 hash function with the inputs given above and based on that it will generate the hash function value that will be the checksum value for my coding..

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• python parallel computing: split keyspace to give each node a range to work on

  - by MatToufoutu

  My question is rather complicated for me to explain, as i'm not really good at maths, but i'll try to be as clear as possible. I'm trying to code a cluster in python, which will generate words given a charset (i.e. with lowercase: aaaa, aaab, aaac, ..., zzzz) and make various operations on them. I'm searching how to calculate, given the charset and the number of nodes, what range each node should work on (i.e.: node1: aaaa-azzz, node2: baaa-czzz, node3: daaa-ezzz, ...). Is it possible to make an algorithm that could compute this, and if it is, how could i implement this in python? I really don't know how to do that, so any help would be much appreciated

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• Require help with program for edutainment game

  - by Ender

  I am working on a factorisation problem and for small numbers it is working well. I've been able to calculate the factors (getting the answers from Wolfram Alpha) for small numbers, like the one on the Wikipedia page (5959). Along with the Wikipedia page I have been following this guide. Once again, as my Math knowledge is pretty poor I cannot follow what I need to do next. EDIT: It finally works! I'll post the working code up here once I've got it fully working so that others in my predicament can learn from it.

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• Animate a e.Graphics.DrawLine with arrowhead

  - by Fer

  I need to "animate" an arrow. It can go in any direction (up, down, left, right and diagonals) and the arrowhead will be at the end. It needs to appear as if it is growing from orgin to the end. To make matters more complicated it has to be in a user control so it is possible to add to the controls collection in the forms and remove it to delete it from the screen, and its background is really transparent (no color.transparent) so i can't paint the background to "clear" the previous line. I have it static already (drawn from origin to end) but i can't animate it. I tried to add a timer in the user control but I fail to get a correct algorithm to calculate the intermediate ends of the line while it is growing. Any help would be appreciated. Thanks

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• JAVA: How do I accept input during a certain period of time only

  - by sebrock

  Im trying to do a simple game where I continually need input from players. This needs to happen during a certain time period only. Everything that is sent after that will be discarded. After the time period a new game starts. So: Start game Wait for input from all players during 10 seconds 10 secs no more input Calculate the winner and do some stuff Goto 1. I was thinking using a timer and timertask to keep track of time and maybe use a boolean variable that changes from "open" to "closed" after 10 seconds? Please give me some advise on this.

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• Who owes who money optimisation problem

  - by Francis

  Say you have n people, each who owe each other money. In general it should be possible to reduce the amount of transactions that need to take place. i.e. if X owes Y £4 and Y owes X £8, then Y only needs to pay X £4 (1 transaction instead of 2). This becomes harder when X owes Y, but Y owes Z who owes X as well. I can see that you can easily calculate one particular cycle. It helps for me when I think of it as a fully connected graph, with the nodes being the amount each person owes. Problem seems to be NP-complete, but what kind of optimisation algorithm could I make, nevertheless, to reduce the total amount of transactions? Doesn't have to be that efficient, as N is quite small for me.

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• Make a <div> square when there is a dynamically changing width based on percentage

  - by Nate

  I am working on a web app that will generate an NxN grid based on the user's selection of N. I want the total width of the grid to be relative (ie 100% of the available space) so that users can print on various paper sizes. I can easily calculate the width of the squares in the grid by % (ie: 100%/N), but I am having issues calculating the height. The height of a web page is always going to be infinite unless I artificially limit it which, like I said, I don't want to do. How can I make the squares in my grid be square versus rectangular when the height and width constraints of my grid are dynamic and not square? Thanks in advance!

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• Why would I want to have a non-standard attribute?

  - by dontWatchMyProfile

  The documentation on Core Data entities says: You might implement a custom class, for example, to provide custom accessor or validation methods, to use non-standard attributes, to specify dependent keys, to calculate derived values, or to implement any other custom logic. I stumbled over the non-standard attributes claim. It's just a guess: If my attribute is anything other than NSString, NSNumber or NSDate I will want to have a non-standard Attribute with special setter and getter methods? So, for example, if I wanted to store an image, this would be a non-standard Attribute with type NSData and a special method, say -(void)setImageWithFileURL:(NSURL*)url which then pulls the image data from the file, puts in in an NSData and assigns it to core data? Or did I get that wrong?

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