Let \$i= 1 , ... , n\$ and \$j= 1, .... , p\$ and let \$x_{ij}\$ a matrix \$n \times p\$, and \$D\$ is a diagonal matrix \$n \times n\$ We have this equation \$N = X^T D X\$ , where N is a \$p \times p\$ matrix. I need to write N as a summation form, any help please; my code in R and in summati...

I'm writing code to create a list of new areas for patches of conserved land within a watershed based on the current size distribution of conserved land patches that are in the watershed now. I'm generating a new random area based on a normal pdf fitted to the log-transformed distribution of th...

Within our application I need to work a lot with simple Ids (just integers). They are used to make queries against a database. For performance reasons I don't want to materialize them to Entities before the query. Example: // not really *that* static typed public void DoQuery(int userId, int ...

I was asked to implement a minimal vi(vi like) text editor in an interview recently. I had to implement display lines,insert lines, delete lines, redo and undo. I used stacks to store recently run commands and recently deleted lines. In the redo() command I find recentCommands stack to be alway...

I have a table that look like this ID NIP SHIFT DATE 289305 01000267 M 2015-12-01 00:00:00.000 289306 01000267 P 2015-12-01 00:00:00.000 289307 01000267 S 2015-12-01 00:00:00.000 289127 01020358 M 2015-12-01 00:00:00.000 289128 01020358 P 2015-12-01 00:00...

I am writing a jQuery plugin that has methods which I believe can be called either with .call or by passing them an object directly. I am trying to decide which one is better practice, and which one should be used for what context. Here's what I'm working with using .call: ;(function( $, wind...

Can anyone tell me why the badge icons in codereview shows differently than other stackexchange sites? Is there any specific meaning for it?

Trying to learn linked lists so I can answer interview questions. Even though I've seen plenty of tutorials to understand how they supposedly work, I don't know if I am doing a good job because I have no one to get feedback from. Here is my attempt. class Node(object): def __init__(self, da...

Here's a program I made for estimating a double integral over a general region. It's pretty accurate, but it's VERY, VERY slow. (Getting an accurate enough result takes about 30 seconds) Here's the code; the lines are indented just for readability. ClrHome Input "Surface: ",Str0 Str0→Y₈ Input "...

I'm working on a programming challenge and the question is as follows: Once Max found an electronic calculator from his grandfather Dovlet's chest. He noticed that the numbers were written with seven-segment indicators (https://en.wikipedia.org/wiki/Seven-segment_display). Max starts to type ...

I receive a string with a lot of characters that I don't need and I am trying to remove them and replace them with characters that I am able to work with. My current structure has me redefining the var multiple times which I feel is not efficient and can probably be done better. Please let me k...

Can you review the code? #include <stdio.h> #include <pthread.h> #include <windows.h> #include "bin/include/pthread.h" #include "bin/include/sched.h" #include "bin/include/semaphore.h" #define TCOUNT 10 #define WATCH_COUNT 12 int count = 0; pthread_mutex_t count_mutex = PTHREAD_MUTEX_INITIAL...

I was recently implementing exoplayer in my app to stream an mp3 file. I wanted to replace it with audioTrack class where I feeded an raw inputStream of bytes into the audioTrack. But there was no datasource availble in exoplayer where it could take a raw inputstream as a parameter. So I created ...

import java.util.Scanner; public class BasicTranformSixteenToEight { public static void toBinaryTransform(int n, char[][] arry, String[] arryBinaryStr) { String[] arryOctalStr = new String[10]; String str = ""; StringBuilder octalStb = new StringBuilder();...

public class EvenOddNumberPrinter {       private static class NumberPrinter {           // To check if even number is printed or not.         private boolean isEvenPrinted = true;           public void printOdd(int number) throws InterruptedException {             // Get a lock on Number...

I've tried to practice performance management while dealing with massive amount of dynamic DOM elements. Please criticize my flaws, and explain how could this perform better focusing mainly on creating elements, displaying them on screen and hiding them when they are not needed anymore. Please ...

Awhile ago I created a program that unlocked spreadsheets, for a better understanding of what happens when it's run, see here. I decided to rewrite it again, and go for a more OOP approach.. My questions being, what can be done better here, Is a module better then a class in this program, and a...

Well considering the following function: def test_func(all_copies, checker): bad_copies = set(c[0] for c in itertools.permutations(all_copies, 2) if not checker(*c)) all_copies = [c for c in all_copies if c not in bad_copies] return all_copies This function basically checks (and re...

im following a tutorial from a guy called Max Wihlborg here's the video: https://www.youtube.com/watch?v=uU5YPIvJ24Y now, my problem. I wrote everything exactly the same as him, but when he went ahead to test it, his worked but mine didnt. i probably made a writing mistake if you could help me ou...

Currently I have an app that have many stores. Each store can have several products. Whom again can have many product attributes assigned to them. For instance a shirt is a product, and size and color would be an attribute. What this method does is add that product with it attributes to the cart...

I am trying to write the following code which enables the user to enter a student's details (username, firstname, surname) as well their grades (there can be one grade or several). The code can also show the students entered and their marks. This is what I have so far but I am having issues with...