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  • How is programming affected by spatial aptitude?

    - by natli
    The longer I work on a project, the less clear it becomes. It's like I cannot seperate various classes/objects anymore in my head. Everything starts mixing up, and it's extremely hard to take it all apart again. I start putting functions in classes where they really don't belong, and make silly mistakes such as writing code that I later find was 100% obsolete; things are no longer clearly mappable in my head. It isn't until I take a step back for several hours (or days somtimes!) that I can actually see what's going on again, and be productive. I usually try to fight through this, I am so passionate about coding that I wouldn't for the life of me know what else I could be doing. This is when stuff can get really weird, I get so up in my head that I sort of lose touch with reality (to some extent) in that various actions, such as pouring a glass of water, no longer happen on a concious level. It happens on auto pilot, during which pretty much all of my concious concentration (is that even a thing?) is devoted to borderline pointless problem solving (trying to seperate elements of code). It feels like a losing battle. So I took an IQ test a while ago (Wechsler Adult Intelligence Scale I believe it was) and it turned out my Spatial Aptitude was quite low. I still got a decent score, just above average, so I won't have to poke things with a stick for a living, but I am a little worried that this is such a handicap when writing/engineering computer programs that I won't ever be able to do it seriously or professionally. I am very much interested in what other people think of this.. could a low spatial aptitude be the cause of the above described problems? Maybe I should be looking more along the lines of ADD or something similar, because I did get diagnosed with ADD at the age of 17 (5 years ago) but the medicine I received didn't seem to affect me that much so I never took it all that serious. Sorry if I got a little off topic there, I know this is not a mental help board, the question should be clear; How is programming affected by spatial aptitude? As far as I know people are born with low/med/high spatial aptitude, so I think it's interesting to find out if the more fortunate are better programmers by birth right.

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  • Should I continue to pursue programming based on my experience?

    - by El Be
    The reason I ask this question is because I am not sure my troubles come from a lack of confidence, or something much deeper like lack of passion. I'm hoping experienced programmers and developers can help identify the cause of my troubles. To be brief my undergraduate major was in Computer Science, but in a small school and I had the highest gpa in my year in computer science. The first time I ever programmed was once in the 5th grade (using logo) and when I was a freshman in college. I enjoyed programming when I was in school. Then I did an internships where I was expected to produce image processing software and program microchips. I was unsuccessful and produced little results and I hated the job, because I had to figure out everything for myself, did not have any help, and there was a lot of pressure to produce results. Although I tried I could not figure out what to do and was stuck all the time and made me dislike the job. When the internship ended I went to a PhD program for computer science at a prestigious computer science school. I had a very hard time with the course, met people who have been programming since they were 6 and made plenty of applications in their spare time (which I never did, although I tried). I even met many sophomores who understood more than I did. The combination of this and other things have made me feel that programming is not for me, but sometimes I consider a career in programming. I still consider programming as a career because of the career potential (not only just because of money). Based on my experience do you believe my confidence has just been shaken and I should continue to prepare for a programming career, or do you see a lack of passion and it would make it tough to continue programming. thank you for reading and for your advice Thank you for everyone's advice so far! Also: I dropped out of the ph.D program for computer science and switched to a master's in computer graphics. Its more applied, but I still find it hard to be motivated (due to either lack of confidence or passion), but since programming is such a big field I am looking for that niche area that I feel good programming in.

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  • How can we improve overall Programmer Education & Training?

    - by crosenblum
    Last week, I was just viewing this amazing interview by Kevin Rose of Phillip Rosedale, of Second Life. And they had an amazing discussion about how to find, hire and identify good programmer's, and how hard it is to find good ones. Which has lead me to really think about the way we programmer's learn, are taught. For a majority of us, myself included, we are self-taught. Which is great about being a programmer, anyone can learn and develop skills. But this also means, that there is no real standards of what a good programmer is/are, and what kind of environment's encourage the growth of programming skills. This isn't so much a question, but just a desire in me, to see how we can change the culture of programming, and the manager's of programming, so that education and self-improvement is encouraged. There are a lot of avenue's for continued education, youtube videos, books, conferences, but because of the experiental nature of what we do, it isn't always clear what's important to learn and to master. Let's look at the The Joel 12 Steps. The Joel Test Do you use source control? Can you make a build in one step? Do you make daily builds? Do you have a bug database? Do you fix bugs before writing new code? Do you have an up-to-date schedule? Do you have a spec? Do programmers have quiet working conditions? Do you use the best tools money can buy? Do you have testers? Do new candidates write code during their interview? Do you do hallway usability testing? I think all of these have important value, but because of something I call the Experiential Gap, if a programmer or manager has never experienced any of the negative consequences for not having done items on the list, they will never see the need to do any of them. The Experiental Gap, is my basic theory, that each of us has different jobs and different experiences. So for some of us, that have always worked with dozens of programmer's, source control is a must have. But for people who have always been the only programmer, they can not imagine the need for source control. And it's because of this major flaw in how we learn, that we evaluate people by what best practices they do or not do, and the reason for either can start a flame war. We always evaluate people in our field by what they do, and think "Oh if this guy/gal isn't doing xyz best practice, he/she can't be a good programmer, so let's not waste time or energy talking to them." This is exactly why we have so many programming flame wars, that it becomes, because of the Experiental Gap, we can't imagine people not having made the decisions that we have had to made. So this has lead me to think, that we totally need to rethink how we train, educate and manage programmer's. For example, what percentage of you have had encouragement by your manager's to go to conferences, and even have them pay for it? For me, and a lot of people, this is extremely rare, a lot of us would love to go to conferences, to learn more, but the money ain't there to do that. So the point of this question is really to spark a lot of how can we train, learn and manage better? How can we create a new culture of learning that doesn't insult people for not having the same job experiences. Yes we all have jobs and work to do, but our ability to do our jobs well, depends on our desire, interest and support in improving our mastery of our skills. Right now, I see our culture being rather disorganized, we support the elite, but those tons of us that want to get better, just don't have enough support to learn and improve ourselves. I mean, do we as an industry, want to be perceived as just replaceable cogs? Thank you...

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  • Collision between sprites in game programming?

    - by Lyn Maxino
    I've since just started coding for an android game using eclipse. I've read Beginning Android Game Programming and various other e-books. Recently, I've encountered a problem with collision between sprites. I've used this code template for my program. package com.project.CAI_test; import java.util.Random; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Rect; public class Sprite { // direction = 0 up, 1 left, 2 down, 3 right, // animation = 3 back, 1 left, 0 front, 2 right int[] DIRECTION_TO_ANIMATION_MAP = { 3, 1, 0, 2 }; private static final int BMP_ROWS = 4; private static final int BMP_COLUMNS = 3; private static final int MAX_SPEED = 5; private GameView gameView; private Bitmap bmp; private int x = 0; private int y = 0; private int xSpeed; private int ySpeed; private int currentFrame = 0; private int width; private int height; public Sprite(GameView gameView, Bitmap bmp) { this.width = bmp.getWidth() / BMP_COLUMNS; this.height = bmp.getHeight() / BMP_ROWS; this.gameView = gameView; this.bmp = bmp; Random rnd = new Random(); x = rnd.nextInt(gameView.getWidth() - width); y = rnd.nextInt(gameView.getHeight() - height); xSpeed = rnd.nextInt(MAX_SPEED * 2) - MAX_SPEED; ySpeed = rnd.nextInt(MAX_SPEED * 2) - MAX_SPEED; } private void update() { if (x >= gameView.getWidth() - width - xSpeed || x + xSpeed <= 0) { xSpeed = -xSpeed; } x = x + xSpeed; if (y >= gameView.getHeight() - height - ySpeed || y + ySpeed <= 0) { ySpeed = -ySpeed; } y = y + ySpeed; currentFrame = ++currentFrame % BMP_COLUMNS; } public void onDraw(Canvas canvas) { update(); int srcX = currentFrame * width; int srcY = getAnimationRow() * height; Rect src = new Rect(srcX, srcY, srcX + width, srcY + height); Rect dst = new Rect(x, y, x + width, y + height); canvas.drawBitmap(bmp, src, dst, null); } private int getAnimationRow() { double dirDouble = (Math.atan2(xSpeed, ySpeed) / (Math.PI / 2) + 2); int direction = (int) Math.round(dirDouble) % BMP_ROWS; return DIRECTION_TO_ANIMATION_MAP[direction]; } public boolean isCollition(float x2, float y2) { return x2 > x && x2 < x + width && y2 > y && y2 < y + height; } } The above code only detects collision between the generated sprites and the surface border. What I want to achieve is a collision detection that is controlled by the update function without having to change much of the coding. Probably several lines placed in the update() function. Tnx for any comment/suggestion.

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  • Reading graph inputs for a programming puzzle and then solving it

    - by Vrashabh
    I just took a programming competition question and I absolutely bombed it. I had trouble right at the beginning itself from reading the input set. The question was basically a variant of this puzzle http://codercharts.com/puzzle/evacuation-plan but also had an hour component in the first line(say 3 hours after start of evacuation). It reads like this This puzzle is a tribute to all the people who suffered from the earthquake in Japan. The goal of this puzzle is, given a network of road and locations, to determine the maximum number of people that can be evacuated. The people must be evacuated from evacuation points to rescue points. The list of road and the number of people they can carry per hour is provided. Input Specifications Your program must accept one and only one command line argument: the input file. The input file is formatted as follows: the first line contains 4 integers n r s t n is the number of locations (each location is given by a number from 0 to n-1) r is the number of roads s is the number of locations to be evacuated from (evacuation points) t is the number of locations where people must be evacuated to (rescue points) the second line contains s integers giving the locations of the evacuation points the third line contains t integers giving the locations of the rescue points the r following lines contain to the road definitions. Each road is defined by 3 integers l1 l2 width where l1 and l2 are the locations connected by the road (roads are one-way) and width is the number of people per hour that can fit on the road Now look at the sample input set 5 5 1 2 3 0 3 4 0 1 10 0 2 5 1 2 4 1 3 5 2 4 10 The 3 in the first line is the additional component and is defined as the number of hours since the resuce has started which is 3 in this case. Now my solution was to use Dijisktras algorithm to find the shortest path between each of the rescue and evac nodes. Now my problem started with how to read the input set. I read the first line in python and stored the values in variables. But then I did not know how to store the values of the distance between the nodes and what DS to use and how to input it to say a standard implementation of dijikstras algorithm. So my question is two fold 1.) How do I take the input of such problems? - I have faced this problem in quite a few competitions recently and I hope I can get a simple code snippet or an explanation in java or python to read the data input set in such a way that I can input it as a graph to graph algorithms like dijikstra and floyd/warshall. Also a solution to the above problem would also help. 2.) How to solve this puzzle? My algorithm was: Find shortest path between evac points (in the above example it is 14 from 0 to 3) Multiply it by number of hours to get maximal number of saves Also the answer given for the variant for the input set was 24 which I dont understand. Can someone explain that also. UPDATE: I get how the answer is 14 in the given problem link - it seems to be just the shortest path between node 0 and 3. But with the 3 hour component how is the answer 24 UPDATE I get how it is 24 - its a complete graph traversal at every hour and this is how I solve it Hour 1 Node 0 to Node 1 - 10 people Node 0 to Node 2- 5 people TotalRescueCount=0 Node 1=10 Node 2= 5 Hour 2 Node 1 to Node 3 = 5(Rescued) Node 2 to Node 4 = 5(Rescued) Node 0 to Node 1 = 10 Node 0 to Node 2 = 5 Node 1 to Node 2 = 4 TotalRescueCount = 10 Node 1 = 10 Node 2= 5+4 = 9 Hour 3 Node 1 to Node 3 = 5(Rescued) Node 2 to Node 4 = 5+4 = 9(Rescued) TotalRescueCount = 9+5+10 = 24 It hard enough for this case , for multiple evac and rescue points how in the world would I write a pgm for this ?

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  • Box2d: Maximum possible linear velocity?

    - by Rosarch
    I think I've configured Box2d to have some sort of maximum velocity for any body, but I'm not sure. I apply an impulse like (100000000, 100000000), and the body moves just as fast as (100, 100) - which is not that fast at all. My game is a top-down 2d. Here is some code that may be relevant: private readonly Vector2 GRAVITY = new Vector2(0, 0); public void initializePhysics(ContactReporter contactReporter) { world = new World(GRAVITY, true); IContactListener contactListener = contactReporter; world.ContactListener = contactListener; } public void Update(GameTime gameTime) { // ... worldState.PhysicsWorld.Step((float)gameTime.ElapsedGameTime.TotalSeconds, 10, 10); //... }

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  • Linear Layout and weight in Android

    - by Janusz
    I always read about this funny weight value in the Android documentations. Now I want to try it for the first time but it isn't working at all. As I understand it from the documentations this layout: <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="horizontal"> <Button android:text="Register" android:id="@+id/register" android:layout_width="wrap_content" android:layout_height="wrap_content" android:padding="10dip" weight="1" /> <Button android:text="Not this time" android:id="@+id/cancel" android:layout_width="wrap_content" android:layout_height="wrap_content" android:padding="10dip" weight="1" /> </LinearLayout> should create two buttons that are horizontally aligned and share the space equally. The problem is the two buttons don't grow to fill the space. The result is something like this: I would like the buttons to grow and fill the whole line.

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  • SVG -> WPF linear gradient

    - by Otaku
    Does anyone know if there is an equilant attribute of SVG's "gradientUnits=userSpaceOnUse" in WPF for a LinearGradientBrush? I can't seem to find this. If not, does anyone know about how to calculate it in (C# or VB.NET)? For example if I have a StartPoint of 0,0 and EndPoint of 1,1 on a Rectangle that is 100x100, the angle is 45 degrees. However, when I change either the width or height of the Rectangle, for example Width=150, the axis is no longer at 45 degrees. How could I calculate to keep the angle at 45 degrees in a rectangle that is not a square so that it runs from bottom left to top right corner for a middle gradientstop.

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  • print a linear linked list into a table

    - by user1796970
    I am attempting to print some values i have stored into a LLL into a readable table. The data i have stored is the following : DEBBIE STARR F 3 W 1000.00 JOAN JACOBUS F 9 W 925.00 DAVID RENN M 3 H 4.75 ALBERT CAHANA M 3 H 18.75 DOUGLAS SHEER M 5 W 250.00 SHARI BUCHMAN F 9 W 325.00 SARA JONES F 1 H 7.50 RICKY MOFSEN M 6 H 12.50 JEAN BRENNAN F 6 H 5.40 JAMIE MICHAELS F 8 W 150.00 i have stored each firstname, lastname, gender, tenure, payrate, and salary into their own List. And would like to be able to print them out in the same format that they are viewed on the text file i read them in from. i have messed around with a few methods that allow me to traverse and print the Lists, but i end up with ugly output. . . here is my code for the storage of the text file and the format i would like to print out: public class Payroll { private LineWriter lw; private ObjectList output; ListNode input; private ObjectList firstname, lastname, gender, tenure, rate, salary; public Payroll(LineWriter lw) { this.lw = lw; this.firstname = new ObjectList(); this.lastname = new ObjectList(); this.gender = new ObjectList(); this.tenure = new ObjectList(); this.rate = new ObjectList(); this.salary = new ObjectList(); this.output = new ObjectList(); this.input = new ListNode(); } public void readfile() { File file = new File("payfile.txt"); try{ Scanner scanner = new Scanner(file); while(scanner.hasNextLine()) { String line = scanner.nextLine(); Scanner lineScanner = new Scanner(line); lineScanner.useDelimiter("\\s+"); while(lineScanner.hasNext()) { firstname.insert1(lineScanner.next()); lastname.insert1(lineScanner.next()); gender.insert1(lineScanner.next()); tenure.insert1(lineScanner.next()); rate.insert1(lineScanner.next()); salary.insert1(lineScanner.next()); } } }catch(FileNotFoundException e) {e.printStackTrace();} } public void printer(LineWriter lw) { String msg = " FirstName " + " LastName " + " Gender " + " Tenure " + " Pay Rate " + " Salary "; output.insert1(msg); System.out.println(output.getFirst()); System.out.println(" " + firstname.getFirst() + " " + lastname.getFirst() + "\t" + gender.getFirst() + "\t" + tenure.getFirst() + "\t" + rate.getFirst() + "\t" + salary.getFirst()); } }

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  • Linear layout and custom dialog

    - by DixieFlatline
    The button doesn't show in this layout(code below),image and textview are shown. I tried using relative layout but that doesn't help either. I'm testing it on 1.5 emulator. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/layout_root" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:padding="10dp" > <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/neki" android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="fill_parent" > <ImageView android:id="@+id/image" android:layout_width="wrap_content" android:layout_height="fill_parent" android:layout_marginRight="10dp" /> <TextView android:id="@+id/text" android:layout_width="wrap_content" android:layout_height="fill_parent" android:textColor="#FFF" android:text="Some text " /> </LinearLayout> <Button android:id="@+id/gumbek" android:text="V redu" android:typeface="serif" android:textStyle="bold" android:layout_width="fill_parent" android:layout_height="wrap_content" /> </LinearLayout>

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  • Scared of Calculus - Required to pass Differential Calculus as part of my Computer science major

    - by ke3pup
    Hi guys I'm finishing my Computer science degree in university but my fear of maths (lack of background knowledge) made me to leave all my maths units til' the very end which is now. i either take them on and pass or have to give up. I've passed all my programming units easily but knowing my poor maths skills won't do i've been staying clear of the maths units. I have to pass Differential Calculus and Linear Algebra first. With a help of book named "Linear Algebra: A Modern Introduction" i'm finding myself on track and i think i can pass the Linear Algebra unit. But with differential calculus i can't find a book to help me. They're either too advanced or just too simple for what i have to learn. The things i'm required to know for this units are: Set notation, the real number line, Complex numbers in cartesian form. Complex plane, modulus. Complex numbers in polar form. De Moivre’s Theorem. Complex powers and nth roots. Definition of ei? and ez for z complex. Applications to trigonometry. Revision of domain and range of a function Working in R3. Curves and surfaces. Functions of 2 variables. Level curves.Partial derivatives and tangent planes. The derivative as a difference quotient. Geometric significance of the derivative. Discussion of limit. Higher order partial derivatives. Limits of f(x,y). Continuity. Maxima and minima of f(x,y). The chain rule. Implicit differentiation. Directional derivatives and the gradient. Limit laws, l’Hoˆpital’s rule, composition law. Definition of sinh and cosh and their inverses. Taylor polynomials. The remainder term. Taylor series. Is there a book to help me get on track with the above? Being a student i can't buy too many books hence why i'm looking for a book that covers topics I need to know. The University library has a fairly limited collection which i took as loan but didn't find useful as it was too complex.

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  • Android - Linear Layout arrangement, not positioning as expected

    - by Arun
    The following is my code. I want an interface where I have a single line textbox, a multiline textbox with 2 buttons below. I want the multiline textbox to occupy all the space available after rendering the buttons and textbox. For this I created two LinearLayouts inside the main layout. The first one has vertical orientation with layout_width set to fill_parent. The second one is horizontal with fill_parent again. The first one has a textbox for which I have set the layout_height to fill parent. The second one has two textboxes OK and Cancel. When I run this application I get the UI, but the Buttons are very small (about 5px in height). I have to set the button height manually. What am I doing wrong here. I don't want to hard code the button height. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <LinearLayout android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_weight="1"> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="Name"></TextView> <EditText android:layout_width="fill_parent" android:layout_height="wrap_content"></EditText> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="Contents"></TextView> <EditText android:layout_width="fill_parent" android:layout_height="fill_parent" android:gravity="top" /> </LinearLayout> <LinearLayout android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_weight="1"> <Button android:id="@+id/okbutt" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="OK" android:layout_weight="1" /> <Button android:layout_width="fill_parent" android:layout_height="fill_parent" android:text="Cancel" android:layout_weight="1" /> </LinearLayout> Thanks, Arun

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  • Non-Linear Database Retrieval

    - by pws5068
    I'm building an article system, and each article will have one more Tags associated with it (similar to the Tags on this site). The tables are set up something like this: Article_Table Article_ID | Title | Author_ID | Content | Date_Posted | IP ... Tag_Table Tag_ID | Name ... Tag_Intersect_Table Tag_ID | Article_ID Is it possible query an article and all of its associated tags in one database call? If so, how is this done?

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  • WPF Linear Fill

    - by Ben
    Hi, I have found some example code that creates a gradient fill in a WPF rectangle control: <Rectangle Height="{Binding ElementName=txtName}" Width="{Binding ElementName=txtName}"> <Rectangle.Fill> <LinearGradientBrush> <GradientStop Color="Silver" Offset="0.0" /> <GradientStop Color="Black" Offset="0.5" /> <GradientStop Color="white" Offset="1.0" /> </LinearGradientBrush> </Rectangle.Fill> </Rectangle> I have some written some code that displays a collection of ListBox's that contain details from MyObject: <UserControl.Resources> <DataTemplate x:Key="CustomerTemplate"> <Border BorderThickness="2" BorderBrush="Silver" CornerRadius="5" Padding="1" Height="50"> <Grid x:Name="thisGrid"> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto" /> <ColumnDefinition Width="Auto" /> </Grid.ColumnDefinitions> <StackPanel Orientation="Horizontal" > <Image Source="C:\MyImage.jpg" Height="50" Width="100" ></Image> </StackPanel> <Border Grid.Column="1" Margin="0" Padding="0"> <StackPanel Orientation="Vertical"> <TextBlock Name="txtName" Text="{Binding Name}" Background="Silver" Foreground="Black" FontSize="16" FontWeight="Bold" Height="25"/> </StackPanel> </Border> </Grid> </Border> </DataTemplate> </UserControl.Resources> <ListBox ItemsSource="{Binding}" ItemTemplate="{StaticResource CustomerTemplate}" Name="grdList" HorizontalContentAlignment="Stretch" VerticalContentAlignment="Stretch" > </ListBox> I would like to apply the same stlye of fill that i get with the first example, in each of my ListBox's. I can't quite figure out how to do this. Can anyone help? Thanks

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  • Linear feedback shift register?

    - by Mattia Gobbi
    Lately I bumped repeatedly into the concept of LFSR, that I find quite interesting because of its links with different fields and also fascinating in itself. It took me some effort to understand, the final help was this really good page, much better than the (at first) cryptic wikipedia entry. So I wanted to write some small code for a program that worked like a LFSR. To be more precise, that somehow showed how a LFSR works. Here's the cleanest thing I could come up with after some lenghtier attempts (Python): def lfsr(seed, taps): sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor sr, xor = str(xor) + sr[:-1], 0 print sr if sr == seed: break lfsr('11001001', (8,7,6,1)) #example I named "xor" the output of the XOR function, not very correct. However, this is just meant to show how it circles through its possible states, in fact you noticed the register is represented by a string. Not much logical coherence. This can be easily turned into a nice toy you can watch for hours (at least I could :-) def lfsr(seed, taps): import time sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor print time.sleep(0.75) sr, xor = str(xor) + sr[:-1], 0 print sr print time.sleep(0.75) Then it struck me, what use is this in writing software? I heard it can generate random numbers; is it true? how? So, it would be nice if someone could: explain how to use such a device in software development come up with some code, to support the point above or just like mine to show different ways to do it, in any language Also, as theres not much didactic stuff around about this piece of logic and digital circuitry, it would be nice if this could be a place for noobies (like me) to get a better understanding of this thing, or better, to understand what it is and how it can be useful when writing software. Should have made it a community wiki? That said, if someone feels like golfing... you're welcome.

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  • Linear regression confidence intervals in SQL

    - by Matt Howells
    I'm using some fairly straight-forward SQL code to calculate the coefficients of regression (intercept and slope) of some (x,y) data points, using least-squares. This gives me a nice best-fit line through the data. However we would like to be able to see the 95% and 5% confidence intervals for the line of best-fit (the curves below). What these mean is that the true line has 95% probability of being below the upper curve and 95% probability of being above the lower curve. How can I calculate these curves? I have already read wikipedia etc. and done some googling but I haven't found understandable mathematical equations to be able to calculate this. Edit: here is the essence of what I have right now. --sample data create table #lr (x real not null, y real not null) insert into #lr values (0,1) insert into #lr values (4,9) insert into #lr values (2,5) insert into #lr values (3,7) declare @slope real declare @intercept real --calculate slope and intercept select @slope = ((count(*) * sum(x*y)) - (sum(x)*sum(y)))/ ((count(*) * sum(Power(x,2)))-Power(Sum(x),2)), @intercept = avg(y) - ((count(*) * sum(x*y)) - (sum(x)*sum(y)))/ ((count(*) * sum(Power(x,2)))-Power(Sum(x),2)) * avg(x) from #lr Thank you in advance.

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  • Initial conditions with a non-linear ODE in Mathematica

    - by buggy
    Hi, I'm trying to use Mathematica's NDSolve[] to compute a geodesic along a sphere using the coupled ODE: x" - (x" . x) x = 0 The problem is that I can only enter initial conditions for x(0) and x'(0) and the solver is happy with the solution where x" = 0. The problem is that my geodesic on the sphere has the initial condition that x"(0) = -x(0), which I have no idea how to tell mathematica. If I add this as a condition, it says I'm adding True to the list of conditions. Here is my code: s1 = NDSolve[{x1''[t] - (x1[t] * x1''[t] + x2[t] * x2''[t] + x3[t]*x3''[t]) * x1[t] == 0, x2''[t] - (x1[t] * x1''[t] + x2[t] * x2''[t] + x3[t]*x3''[t]) * x2[t] == 0, x3''[t] - (x1[t] * x1''[t] + x2[t] * x2''[t] + x3[t]*x3''[t]) * x3[t] == 0, x1[0] == 1, x2[0] == 0, x3[0] == 0, x1'[0] == 0, x2'[0] == 0, x3'[0] == 1} , { x1, x2, x3}, {t, -1, 1}][[1]] I would like to modify this so that the initial acceleration is not zero but -x(0). Thanks

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  • Non-graphical linearity estimation

    - by aL3xa
    In my previous post, I was looking for correlation ratio (η or η2) routines in R. I was surprised by the fact that no one uses η for linearity checking in the GLM procedures. Let's start form a simple example: how do you check linearity of bivariate correlation? Solely with scatterplot? There are several ways of doing this, one way is to compare linear and non-linear model R2, then to apply F test to seek for significant difference between them. Finally, the question is: How do you check linearity, the "non-grafical" way?

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  • Linear Recurrence for very large n

    - by Android Decoded
    I was trying to solve this problem on SPOJ (http://www.spoj.pl/problems/REC/) F(n) = a*F(n-1) + b where we have to find F(n) Mod (m) where 0 <= a, b, n <= 10^100 1 <= M <= 100000 I am trying to solve it with BigInteger in JAVA but if I run a loop from 0 to n its getting TLE. How could I solve this problem? Can anyone give some hint? Don't post the solution. I want hint on how to solve it efficiently.

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  • Non-Linear color interpolation?

    - by user146780
    If I have a straight line that mesures from 0 to 1, then I have colorA(255,0,0) at 0 on the line, then at 0.3 I have colorB(20,160,0) then at 1 on the line I have colorC(0,0,0). How could I find the color at 0.7? Thanks

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  • How did you get your first programming job?

    - by Gaz
    Hi All, I have some commercial programming experience although it was not my primary role (C# and Java), SCJP 6 cert, some SQL experience and have been doing a lot of Android programming (I have one app with 36,000 downloads). I have a degree in Chemistry and a Diploma in Programming (half a degree made up of 2nd/3rd year uni courses). I'm trying to get my first entry level programmer job but am finding it tough out there.......How did other people get there first jobs in programming?

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  • Solving for the coefficent of linear equations with one known coefficent

    - by CppLearner
    clc; clear all; syms y a2 a3 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % [ 0.5 0.25 0.125 ] [ a2 ] [ y ] % [ 1 1 1 ] [ a3 ] = [ 3 ] % [ 2 4 8 ] [ 6 ] [ 2 ] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% M = [0.5 0.25 0.125; 1 1 1; 2 4 8]; t = [a2 a3 6]; r = [y 3 2]; sol = M * t' s1 = solve(sol(1), a2) % solve for a2 s2 = solve(sol(2), a3) % solve for a3 This is what I have so far. These are my output sol = conj(a2)/2 + conj(a3)/4 + 3/4 conj(a2) + conj(a3) + 6 2*conj(a2) + 4*conj(a3) + 48 s1 = - conj(a3)/2 - 3/2 - Im(a3)*i s2 = - conj(a2) - 6 - 2*Im(a2)*i sol looks like what we would have if we put them back into equation form: 0.5 * a2 + 0.25 * a3 + 0.125 * a4 a2 + a3 + a4 = 3 2*a2 + 4*a3 + 8*a4 = 2 where a4 is known == 6. My problem is, I am stuck with how to use solve to actually solve these equations to get the values of a2 and a3. s2 solve for a3 but it doesn't match what we have on paper (not quite). a2 + a3 + 6 = 3 should yield a3 = -3 - a2. because of the imaginary. Somehow I need to equate the vector solution sol to the values [y 3 2] for each row.

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  • Data frame linear fit in R

    - by user1247384
    This is perhaps a simple question, but I am n00b.Say I have a data frame with a bunch of columns. I need to call lm function over the column 1 and 2, 1 and 3, and so on. So basically I need to loop over all columns and store the results of the fit as I build the model. The problem I am running into is that lm(df[1]~df[2], data = df) doesnt work. In this case df is the data frame object and df[1] is the first column. What is a good way to do this in a loop, as in access the columns of df in an iterative fashion. Thanks.

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