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  • R: preventing unlist to drop NULL values

    - by nico
    I'm running into a strange problem. I have a vector of lists and I use unlist on them. Some of the elements in the vectors are NULL and unlist seems to be dropping them. How can I prevent this? Here's a simple (non) working example showing this unwanted feature of unlist a = c(list("p1"=2, "p2"=5), list("p1"=3, "p2"=4), list("p1"=NULL, "p2"=NULL), list("p1"=4, "p2"=5)) unlist(a) p1 p2 p1 p2 p1 p2 2 5 3 4 4 5

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  • How are iterators and pointers related?

    - by sharptooth
    Code with iterators looks pretty much like code with pointers. Iterators are of some obscure type (like std::vector<int>::iterator for example). What I don't get is how iterators and pointer are related to each other - is an iterator a wrapper around a pointer with overloaded operations to advance to adjacent elements or is it something else?

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  • paintComponent method is not displaying anything on the panel

    - by Captain Gh0st
    I have been trying to debug this for hours. The program is supposed to be a grapher that graphs coordinates, but i cannot get anything to display not even a random line, but if i put a print statement there it works. It is a problem with the paintComponent Method. When I out print statement before g.drawLine then it prints, but it doesn't draw any lines even if i put a random line with coordinates (1,3), (2,4). import java.awt.*; import java.util.*; import javax.swing.*; public abstract class XYGrapher { abstract public Coordinate xyStart(); abstract public double xRange(); abstract public double yRange(); abstract public Coordinate getPoint(int pointNum); public class Paint extends JPanel { public void paintGraph(Graphics g, int xPixel1, int yPixel1, int xPixel2, int yPixel2) { super.paintComponent(g); g.setColor(Color.black); g.drawLine(xPixel1, yPixel1, xPixel2, yPixel2); } public void paintXAxis(Graphics g, int xPixel, int pixelsWide, int pixelsHigh) { super.paintComponent(g); g.setColor(Color.green); g.drawLine(xPixel, 0, xPixel, pixelsHigh); } public void paintYAxis(Graphics g, int yPixel, int pixelsWide, int pixelsHigh) { super.paintComponent(g); g.setColor(Color.green); g.drawLine(0, yPixel, pixelsWide, yPixel); } } public void drawGraph(int xPixelStart, int yPixelStart, int pixelsWide, int pixelsHigh) { JFrame frame = new JFrame(); Paint panel = new Paint(); panel.setPreferredSize(new Dimension(pixelsWide, pixelsHigh)); panel.setMinimumSize(new Dimension(pixelsWide, pixelsHigh)); panel.setMaximumSize(new Dimension(pixelsWide, pixelsHigh)); frame.setLocation(frame.getToolkit().getScreenSize().width / 2 - pixelsWide / 2, frame.getToolkit().getScreenSize().height / 2 - pixelsHigh / 2); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setResizable(false); frame.add(panel); frame.pack(); frame.setVisible(true); double xRange = xRange(); double yRange = yRange(); Coordinate xyStart = xyStart(); int xPixel = xPixelStart - (int) (xyStart.getX() * (pixelsWide / xRange)); int yPixel = yPixelStart + (int) ((xyStart.getY() + yRange) * (pixelsHigh / yRange)); System.out.println(xPixel + " " + yPixel); if(yPixel > 0 && (yPixel < pixelsHigh)) { System.out.println("y"); panel.paintYAxis(panel.getGraphics(), yPixel, pixelsWide, pixelsHigh); } if(xPixel > 0 && (xPixel < pixelsHigh)) { System.out.println("x"); panel.paintXAxis(panel.getGraphics(), xPixel, pixelsWide, pixelsHigh); } for(int i = 0; i>=0; i++) { Coordinate point1 = getPoint(i); Coordinate point2 = getPoint(i+1); if(point2 == null) { break; } else { if(point1.drawFrom() && point2.drawTo()) { int xPixel1 = (int) (xPixelStart + (point1.getX() - xyStart.getX()) * (pixelsWide / xRange)); int yPixel1 = (int) (yPixelStart + (xyStart.getY() + yRange-point1.getY()) * (pixelsHigh / yRange)); int xPixel2 = (int) (xPixelStart + (point2.getX() - xyStart.getX()) * (pixelsWide / xRange)); int yPixel2 = (int) (yPixelStart + (xyStart.getY() + yRange - point2.getY()) * (pixelsHigh / yRange)); panel.paintGraph(panel.getGraphics(), xPixel1, yPixel1, xPixel2, yPixel2); } } } frame.pack(); } } This is how i am testing it is supposed to be a square, but nothing shows up. public class GrapherTester extends XYGrapher { public Coordinate xyStart() { return new Coordinate(-2,2); } public double xRange() { return 4; } public double yRange() { return 4; } public Coordinate getPoint(int pointNum) { switch(pointNum) { case 0: return new Coordinate(-1,-1); case 1: return new Coordinate(1,-1); case 2: return new Coordinate(1,1); case 3: return new Coordinate(-1,1); case 4: return new Coordinate(-1,-1); } return null; } public static void main(String[] args) { new GrapherTester().drawGraph(100, 100, 500, 500); } } Coordinate class so if any of you want to run and try it out. That is all you would need. public class Coordinate { float x; float y; boolean drawTo; boolean drawFrom; Coordinate(double x, double y) { this.x = (float) x; this.y = (float) y; drawFrom = true; drawTo = true; } Coordinate(double x, double y, boolean drawFrom, boolean drawTo) { this.x = (float) x; this.y = (float) y; this.drawFrom = drawFrom; this.drawTo = drawTo; } public double getX() { return x; } public double getY() { return y; } public boolean drawTo() { return drawTo; } public boolean drawFrom() { return drawFrom; } }

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  • improving drawing pythagoras tree

    - by sasquatch90
    Hello. I have written program for drawing pythagoras tree fractal. Can anybody see any way of improving it ? Now it is 120 LOc. I was hoping to shorten it to ~100... import javax.swing.*; import java.util.Scanner; import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import javax.swing.JComponent; public class Main extends JFrame {; public Main(int n) { setSize(900, 900); setTitle("Pythagoras tree"); Draw d = new Draw(n); add(d); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setVisible(true); } private int pow(int n){ int pow = 2; for(int i = 1; i < n; i++){ if(n==0){ pow = 1; } pow = pow*2; } return pow; } public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Give amount of steps: "); int steps = sc.nextInt(); new Main(steps); } } class Draw extends JComponent { private int height; private int width; private int steps; public Draw(int n) { height = 800; width = 800; steps = n; Dimension d = new Dimension(width, height); setMinimumSize(d); setPreferredSize(new Dimension(d)); setMaximumSize(d); } @Override public void paintComponent(Graphics g) { super.paintComponent(g); g.setColor(Color.white); g.fillRect(0, 0, width, height); g.setColor(Color.black); int w = width; int h = height; int x1, x2, x3, x4, x5, y1, y2, y3, y4, y5; int base = w/7; x1 = (w/2)-(base/2); x2 = x1; x3 = (w/2)+(base/2); x4 = x3; x5 = w/2; y1 = (h-(h/15))-base; y2 = h-(h/15); y3 = y2; y4 = y1; y5 = (h-(h/15))-(base+(base/2)); //paint g.drawLine(x1, y1, x2, y2); g.drawLine(x2, y2, x3, y3); g.drawLine(x3, y3, x4, y4); g.drawLine(x1, y1, x4, y4); int n1 = steps; n1--; if(n1>0){ g.drawLine(x1, y1, x5, y5); g.drawLine(x4, y4, x5, y5); paintMore(n1, g, x1, x5, x4, y1, y5, y4); paintMore(n1, g, x4, x5, x1, y4, y5, y1); } } public void paintMore(int n1, Graphics g, double x1_1, double x2_1, double x3_1, double y1_1, double y2_1, double y3_1){ double x1, x2, x3, x4, x5, y1, y2, y3, y4, y5; //counting x1 = x1_1 + (x2_1-x3_1); x2 = x1_1; x3 = x2_1; x4 = x2_1 + (x2_1-x3_1); x5 = ((x2_1 + (x2_1-x3_1)) + ((x2_1-x3_1)/2)) + ((x1_1-x2_1)/2); y1 = y1_1 + (y2_1-y3_1); y2 = y1_1; y3 = y2_1; y4 = y2_1 + (y2_1-y3_1); y5 = ((y1_1 + (y2_1-y3_1)) + ((y2_1-y1_1)/2)) + ((y2_1-y3_1)/2); //paint g.setColor(Color.green); g.drawLine((int)x1, (int)y1, (int)x2, (int)y2); g.drawLine((int)x3, (int)y3, (int)x4, (int)y4); g.drawLine((int)x1, (int)y1, (int)x4, (int)y4); n1--; if(n1>0){ g.drawLine((int)x1, (int)y1, (int)x5, (int)y5); g.drawLine((int)x4, (int)y4, (int)x5, (int)y5); paintMore(n1, g, x1, x5, x4, y1, y5, y4); paintMore(n1, g, x4, x5, x1, y4, y5, y1); } } }

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  • The internal implementation of R's dataset

    - by Yin Zhu
    I am trying to build a data processing program. Currently I use a double matrix to represent the data table, each row is an instance, each column represents a feature. I also have an extra vector as the target value for each instance, it is of double type for regression, it is of integer for classification. I want to make it more general. I am wondering how what kind of structure R uses to store a dataset, i.e. the internal implementation in R.

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  • Idiomatic scheme and generic programming, why only on numbers ?

    - by Skeptic
    Hi, In Scheme, procedures like +, -, *, / works on different types of numbers, but we don't much see any other generic procedures. For example, length works only on list so that vector-length and string-length are needed. I guess it comes from the fact that the language doesn't really offer any mechanism for defining generic procedure (except cond of course) like "type classes" in Haskell or a standardized object system. Is there an idiomatic scheme way to handle generic procedures that I'm not aware of ?

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  • 1136: Incorrect number of arguments. Expected 0.? AS3 Flash Cs4 (Round 2)

    - by charmaine
    (I have asked this before but I dont think I was direct enough with my question and therefore it did not get resolved so here goes again!) I am working through a book called Foundation Actionscript 3.0 Animation, making things move. I am now on Chapter 9 - Collision Detection. On two lines of my code I get the 1135 error, letting me know that I have an incorrect number of arguments. I have highlighted the two areas in which this occurs with asterisks: package { import flash.display.Sprite; import flash.events.Event; public class Bubbles extends Sprite { private var balls:Array; private var numBalls:Number = 10; private var centerBall:Ball; private var bounce:Number = -1; private var spring:Number = 0.2; public function Bubbles() { init(); } private function init():void { balls = new Array(); ***centerBall = new Ball(100, 0xcccccc);*** addChild(centerBall); centerBall.x = stage.stageWidth / 2; centerBall.y = stage.stageHeight / 2; for(var i:uint = 0; i < numBalls; i++) { ***var ball:Ball = new Ball(Math.random() * 40 + 5, Math.random() * 0xffffff);*** ball.x = Math.random() * stage.stageWidth; ball.y = Math.random() * stage.stageHeight; ball.vx = Math.random() * 6 - 3; ball.vy = Math.random() * 6 - 3; addChild(ball); balls.push(ball); } addEventListener(Event.ENTER_FRAME, onEnterFrame); } private function onEnterFrame(event:Event):void { for(var i:uint = 0; i < numBalls; i++) { var ball:Ball = balls[i]; move(ball); var dx:Number = ball.x - centerBall.x; var dy:Number = ball.y - centerBall.y; var dist:Number = Math.sqrt(dx * dx + dy * dy); var minDist:Number = ball.radius + centerBall.radius; if(dist < minDist) { var angle:Number = Math.atan2(dy, dx); var tx:Number = centerBall.x + Math.cos(angle) * minDist; var ty:Number = centerBall.y + Math.sin(angle) * minDist; ball.vx += (tx - ball.x) * spring; ball.vy += (ty - ball.y) * spring; } } } private function move(ball:Ball):void { ball.x += ball.vx; ball.y += ball.vy; if(ball.x + ball.radius > stage.stageWidth) { ball.x = stage.stageWidth - ball.radius; ball.vx *= bounce; } else if(ball.x - ball.radius < 0) { ball.x = ball.radius; ball.vx *= bounce; } if(ball.y + ball.radius > stage.stageHeight) { ball.y = stage.stageHeight - ball.radius; ball.vy *= bounce; } else if(ball.y - ball.radius < 0) { ball.y = ball.radius; ball.vy *= bounce; } } } } I think this is due to the non-existance of a Ball.as, when reading the tutorial I assumed it meant that I had to create a movie clip of a ball on stage and then export it for actionscript with the class name being Ball, however when flicking back through the book I saw that a Ball.as already existed, stating that I may need to use this again later on in the book, this read: package { import flash.display.Sprite; public class Ball extends Sprite { private var radius:Number; private var color:uint; public var vx:Number=0; public var vy:Number=0; public function Ball(radius:Number=40, color:uint=0xff0000) { this.radius=radius; this.color=color; init(); } public function init():void { graphics.beginFill(color); graphics.drawCircle(0, 0, radius); graphics.endFill(); } } } This managed to stop all the errors appearing however, it did not transmit any of the effects from Bubbles.as it just braught a Red Ball on the center of the stage. How would I alter this code in order to work in favour of Bubbles.as? Please Help! Thanks!

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  • Two collections and a for loop. (Urgent help needed) Checking an object variable against an inputted

    - by Elliott
    Hi there, I'm relatively new to java, I'm certain the error is trivial. But can't for the life of me spot it. I have an end of term exam on monday and currently trying to get to grips with past papers! Anyway heregoes, in another method (ALGO_1) I search over elements of and check the value H_NAME equals a value entered in the main. When I attempt to run the code I get a null pointer exception, also upon trying to print (with System.out.println etc) the H_NAME value after each for loop in the snippet I also get a null statement returned to me. I am fairly certain that the collection is simply not storing the data gathered up by the Scanner. But then again when I check the collection size with size() it is about the right size. Either way I'm pretty lost and would appreciate the help. Main questions I guess to ask are: from the readBackground method is the data.add in the wrong place? is the snippet simply structured wrongly? oh and another point when I use System.out.println to check the Background object values name, starttime, increment etc they print out fine. Thanks in advance.(PS im guessing the formatting is terrible, apologies.) snippet of code: for(Hydro hd: hydros){ System.out.println(hd.H_NAME); for(Background back : backgs){ System.out.println(back.H_NAME); if(back.H_NAME.equals(hydroName)){ //get error here public static Collection<Background> readBackground(String url) throws IOException { URL u = new URL(url); InputStream is = u.openStream(); InputStreamReader isr = new InputStreamReader(is); BufferedReader b = new BufferedReader(isr); String line =""; Vector<Background> data = new Vector<Background>(); while((line = b.readLine())!= null){ Scanner s = new Scanner(line); String name = s.next(); double starttime = Double.parseDouble(s.next()); double increment = Double.parseDouble(s.next()); double sum = 0; double p = 0; double nterms = 0; while((s.hasNextDouble())){ p = Double.parseDouble(s.next()); nterms++; sum += p; } double pbmean = sum/nterms; Background SAMP = new Background(name, starttime, increment, pbmean); data.add(SAMP); } return data; } Edit/Delete Message

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  • How would you program Pascal's triangle in R?

    - by Peter Flom
    I am reading, on my own (not for HW) about programming, and one exercise involved programming Pascal's triangle in R. My first idea was to make a list and then append things to it, but that didn't work too well. Then I thought of starting with a vector, and making a list out of that, at the end. Then I thought of making a matrix, and making a list out of that at the end. Not sure which way to even approach this. Any hints? thanks

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  • How to do an alphnumeric sort in R

    - by cbare
    Is there an alphanumeric sort for R? Say I had a character vector like so: > seq.names <- c('abc21', 'abc2', 'abc1', 'abc01', 'abc4', 'abc201', '1b', '1a') I'd like to sort it aphanumerically, so I get back this: c('1a', '1b', 'abc1', 'abc01', 'abc2', 'abc4', 'abc21', 'abc201') Does this exist somewhere, or should I start coding? Thanks, -chris

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  • C++ STL containers

    - by cambr
    Different STL containers like vector, stack, set, queue, etc support different access methods on them. If you are coding for example in Notepad++ or vim, you have to continuously refer to the documentation to see what all methods are available, atleast I have to. Is there some good way of remembering which container supports which methods??

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  • Help with code optimization

    - by Ockonal
    Hello, I've written a little particle system for my 2d-application. Here is raining code: // HPP ----------------------------------- struct Data { float x, y, x_speed, y_speed; int timeout; Data(); }; std::vector<Data> mData; bool mFirstTime; void processDrops(float windPower, int i); // CPP ----------------------------------- Data::Data() : x(rand()%ScreenResolutionX), y(0) , x_speed(0), y_speed(0), timeout(rand()%130) { } void Rain::processDrops(float windPower, int i) { int posX = rand() % mWindowWidth; mData[i].x = posX; mData[i].x_speed = WindPower*0.1; // WindPower is float mData[i].y_speed = Gravity*0.1; // Gravity is 9.8 * 19.2 // If that is first time, process drops randomly with window height if (mFirstTime) { mData[i].timeout = 0; mData[i].y = rand() % mWindowHeight; } else { mData[i].timeout = rand() % 130; mData[i].y = 0; } } void update(float windPower, float elapsed) { // If this is first time - create array with new Data structure objects if (mFirstTime) { for (int i=0; i < mMaxObjects; ++i) { mData.push_back(Data()); processDrops(windPower, i); } mFirstTime = false; } for (int i=0; i < mMaxObjects; i++) { // Sleep until uptime > 0 (To make drops fall with randomly timeout) if (mData[i].timeout > 0) { mData[i].timeout--; } else { // Find new x/y positions mData[i].x += mData[i].x_speed * elapsed; mData[i].y += mData[i].y_speed * elapsed; // Find new speeds mData[i].x_speed += windPower * elapsed; mData[i].y_speed += Gravity * elapsed; // Drawing here ... // If drop has been falled out of the screen if (mData[i].y > mWindowHeight) processDrops(windPower, i); } } } So the main idea is: I have some structure which consist of drop position, speed. I have a function for processing drops at some index in the vector-array. Now if that's first time of running I'm making array with max size and process it in cycle. But this code works slower that all another I have. Please, help me to optimize it. I tried to replace all int with uint16_t but I think it doesn't matter.

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  • c++ program debugged well with Cygwin4 (under Netbeans 7.2) but not with MinGW (under QT 4.8.1)

    - by GoldenAxe
    I have a c++ program which take a map text file and output it to a graph data structure I have made, I am using QT as I needed cross-platform program and GUI as well as visual representation of the map. I have several maps in different sizes (8x8 to 4096x4096). I am using unordered_map with a vector as key and vertex as value, I'm sending hash(1) and equal functions which I wrote to the unordered_map in creation. Under QT I am debugging my program with QT 4.8.1 for desktop MinGW (QT SDK), the program works and debug well until I try the largest map of 4096x4096, then the program stuck with the following error: "the inferior stopped because it received a signal from operating system", when debugging, the program halt at the hash function which used inside the unordered_map and not as part of the insertion state, but at a getter(2). Under Netbeans IDE 7.2 and Cygwin4 all works fine (debug and run). some code info: typedef std::vector<double> coordinate; typedef std::unordered_map<coordinate const*, Vertex<Element>*, container_hash, container_equal> vertexsContainer; vertexsContainer *m_vertexes (1) hash function: struct container_hash { size_t operator()(coordinate const *cord) const { size_t sum = 0; std::ostringstream ss; for ( auto it = cord->begin() ; it != cord->end() ; ++it ) { ss << *it; } sum = std::hash<std::string>()(ss.str()); return sum; } }; (2) the getter: template <class Element> Vertex<Element> *Graph<Element>::getVertex(const coordinate &cord) { try { Vertex<Element> *v = m_vertexes->at(&cord); return v; } catch (std::exception& e) { return NULL; } } I was thinking maybe it was some memory issue at the beginning, so before I was thinking of trying Netbeans I checked it with QT on my friend pc with a 16GB RAM and got the same error. Thanks.

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  • Copying from istream never stops

    - by the_drow
    This bit of code runs infinitely: copy(istream_iterator<char>(cin), istream_iterator<char>(), back_inserter(buff)); The behavior I was expecting is that it will stop when I press enter. However it doesn't. buff is a vector of chars.

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  • Indexing one-dimensional numpy.array as matrix

    - by Alain
    I am trying to index a numpy.array with varying dimensions during runtime. To retrieve e.g. the first row of a n*m array a, you can simply do a[0,:] However, in case a happens to be a 1xn vector, this code above returns an index error: IndexError: too many indices As the code needs to be executed as efficiently as possible I don't want to introduce an if statement. Does anybody have a convenient solution that ideally doesn't involve changing any data structure types?

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  • Standard library function in R for finding the mode?

    - by Nick
    In statistical language R, mean() and median() are standard functions which do what you'd expect. mode() tells you the internal storage mode of the R object, not the value that occurs the most in its argument. But surely there is a standard library function that implements mode for a vector (or list).

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