Questions tagged [matrix]

In mathematics, a matrix (plural matrices) is a rectangular array of numbers, symbols, or expressions, arranged in rows and columns. The individual items in a matrix are called its elements or entries.

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Matrix Transpose in Golang

I have write a normal programm "Transpose the matrix" in go. Suppose input are always correct. I also read the article An Efficient Matrix Transpose in CUDA C/C++. So I keen to know how I can use Go-...
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3answers
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Rotate square matrix clockwise by 90degrees

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1answer
72 views

Matrix class with overloaded `operator[]`

I have implemented a Matrix class that allocates memory using unique_ptr. How to make it more diverse and optimized in terms of memory usage and efficiency? ...
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R solution to max product in matrix for four adjacent numbers (Euler 11)

Background This is solution to Problem 11 on Project Euler that is concerned with finding largest product of four adjacent numbers in the provided grid. Other than solving the problem I was also ...
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117 views

Matrix with spiral increasing values

This generates a square matrix with spiral inward increasing values. How can I reduce this code? Input Number = 3 Output 1 2 3 8 9 4 7 6 5 ...
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1answer
44 views

Connect Four – get all diagonal and anti-diagonal rows

I started learning python with the connect four game. Now I'm searching for the best way to get all diagonal and anti-diagonal rows of a matrix. It should work with any 2-dimensional matrix. My code ...
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1answer
122 views

Count number of unique adjacent cells in a matrix

I want to write an algorithm to count how many islands are in a given matrix. Consider for example: ...
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1answer
89 views

Finding shortest path in matrix

Given an N x N matrix of positive integers, I need to find the shortest path from the first cell of matrix to the last cell of matrix. I can move exactly x steps from any cell, where x is the value of ...
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1answer
60 views

Using Python to search a sorted 2D Matrix

Code Problem ...
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80 views

General matrix class

I have written a matrix class using python, allowing me to perform a variety of operations on matrices. I'm pretty happy with how it performs, and everything works fine. However, I feel like the way I'...
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1answer
62 views

My custom implementation of MATLAB's imdilate

I have been assigned to implement the morphological dilation operation without using MATLAB's imdilate, and I came up with the following solution: ...
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How would you convert this code to best take advantage of CSS transform for panning/zooming?

I am using react-flow-chart for a job project, but it doesn't implement zoom, and I would like to take the reigns and try applying it myself. I took a linear ...
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2answers
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Rotate a matrix, using transposition and reflection

I want to compare two solutions to the following question from Cracking The Coding Interview by Gayle Laakman McDowell : 1.7 Rotate Matrix - Given an image represented by an NxN matrix, where each ...
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356 views

Magic Square (Python)

Problem Write a method to return a boolean if an input grid is magic square. A magic square is a \$NxN\$ square grid (where N is the number of cells on each side) filled with distinct positive ...
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1answer
161 views

overlapping rectangles c#

I had to write code for a competition which calculates sum of the perimeter of three overlapping rectangles in a 2D space. rectangle A and rectangles B and rectangle c is overlapping each other.They ...
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846 views

Python algorithm that converts array-like data into MathJax

I frequently use MathJax, and often I need to write matrices. Since writing matrices using MathJax is very tiresome task, I decided to automate it. Code: ...
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Matrix class in C#

I've been learning C# during my free time in the past months; before that, I was mostly writing Java, so the transition hasn't been too hard, but I've never had my code reviewed or read by someone ...
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Compute angular distances between data points in a matrix

I am having a hard time speeding up a function that I use to compute angular distances between data points in a matrix. More precisely, I want to compute $$\sum_{r=1}^n|\pi - \arccos\left(\frac{(X_{i}-...
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Fast matrix transpose

I would like to improve the naive matrix transpose algorithm by using a cache friendly algorithm. So far there are 4 variants. Iterate over the source matrix: ...
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42 views

Stochastic gradient descent - backpropagation over mini-batches in one go

I have been working through a tutorial on neural networks. I have then been translating the code to java, to help improve my understanding of what the code is doing. The book mentions a way of ...
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2answers
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Large matrix with lots of repetitive fields (C++)

I wrote a timetabling program and I have been using a matrix to check for clashes between courses. Index (i, j) in the matrix ...
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63 views

4×4 cofactor in SSE

The cofactor of a 4×4 matrix can be used to convert a "regular geometry" matrix into the matrix that transforms the normals. It's an alternative to the common inverse-transpose pattern. In this post I ...
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Ruby implementation for Hacker Rank connected cells in a grid

https://www.hackerrank.com/challenges/connected-cell-in-a-grid/problem problem statement: Consider a matrix where each cell contains either a 1 or a 0. Any cell containing a 1 is called a ...
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1answer
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Find the number of pawns available for a rook to capture

I find that very very often with matrix questions, the traversal and comparison part of the solution is very verbose and repetitive. For example, this code (written for a coding challenge) to find ...
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2answers
87 views

Generate a large block diagonal covariance matrix with exponential decay

I am implementing Kalman filtering in R. Part of the problem involves generating a really huge error covariance block-diagonal matrix (dim: 18000 rows x 18000 columns = 324,000,000 entries). We denote ...
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3answers
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Modeling, view and projection transformation using vector and point in homogenous form

I know this is horrible code. This program is for performing modeling, view and projection transformation. The program reads input from scene.txt and outputs the <...
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2answers
129 views

Golang matrix package

I developed a small package to do matrix math. I just learned Go so I may have done it wrong. ...
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1answer
211 views

Getting saddle points of a matrix

My homework assignment: Write a function called saddle that finds saddle points in the input matrix M. For the purposes of this problem, a saddle point is defined as an element whose value is ...
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1answer
158 views

Pad a ragged multidimensional array to rectangular shape

For some machine learning purpose, I need to work with sequences with different lengths. To be able to process efficiently those sequences, I need to process them in batches of size ...
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35 views

Spiral printing elements of a matrix

As I'm learning elixir, I wrote some code for printing elements in the spiral of a matrix(2D array). I was wondering if there is any room for improvements with regards to its performance or ...
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1answer
223 views

Rotate matrix clockWise and counter clockWise

This code is a mix of the same question one time rotating to the right and one time to the left. I tried to simplify the code since I'm struggling with all of the indexing here. https://leetcode.com/...
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1answer
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CUDA matrix class

I started to work on this CUDA C matrix class to learn both the object oriented programming in C++ and to learn CUDA. The initial goal of this project was to make a matrix class that can have almost ...
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1answer
70 views

Generating random sparse matrix

My goal is to generate a large sparse matrix with majority (~99%) zeros and ones. Ideally, I would be working with 10,000 rows and 10,000,000 columns. Additionally, each column is generated as a ...
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1answer
59 views

LeetCode: Transpose Matrix C#

Please review performance https://leetcode.com/problems/transpose-matrix/ Given a matrix A, return the transpose of A. The transpose of a matrix is the matrix flipped over it's main ...
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Striping a matrix concentrically, anticlockwise

Given a matrix you shall stripe the matrix, such that every number that has equal distance to the matrix border will be filled into an array. For examples see code comments. ...
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1answer
72 views

Multiplying a Matrix with its Transpose

Currently, I am in the process of optimizing a MIPS assembly program that takes a n x n matrix and multiplies it with its transpose. I am trying to optimize my matrix calculation algorithm so that it ...
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1answer
36 views

Transposing a square matrix (n x n)

I wish to transpose a square matrix, permanently overwriting it. This is not the same as creating a 2nd matrix with the transposed contents of the 1st matrix. I call the procedure with 3 parameters: ...
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250 views

Python program to solve matrix-chain multiplication

An assignment at school required me to write a Python program for this task: In the matrix-chain multiplication problem, we are given a sequence of matrices ...
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1answer
148 views

GeeksforGeeks: Rotate matrix by 90 degrees

Please review the code readability, I would like to have an easier to follow code. Thanks ...
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1answer
90 views

3-function program computing connected components of a point cloud given a distance matrix

I wrote this code in Haskell (instead of Python) for the educational benefit. Can anyone suggest ways to improve this code? I'm guessing that I'm using fromIntegral...
3
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1answer
64 views

Sums of columns and diagonals of a matrix

I made a simple matrix program that prints some data..I want to know how to reduce amount of lines with some functions or whatever, because there is so much if-s,and for loops. Tried to make ...
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1answer
48 views

Sum of Two Matrices

For a homework assignment, I was asked to do this problem. It worked, but it looks messy in my opinion. I want to know if this is the best way to accomplish this task, and if there can be any ...
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0answers
50 views

Lowest cost path through elements in a matrix

I've developed a program in Python that calculates the lowest possible costing path between two points in a matrix, including the values contained in the start and finish cells. The code is below. ...
2
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1answer
76 views

Computing the difference of the cross-totals of the diagonals of a matrix

I have solved a seemingly easy problem: Given a square matrix, calculate the absolute difference between the sums of its diagonals. For example, the square matrix is shown below: $$\begin{bmatrix}...
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3answers
76 views

Matrix input in N*N form in Python

I am using the below code in Python to input a N*N matrix in its original form: ...
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1answer
139 views

Search for row number of maximum value in matrix column

Background I'm writing code that searches for the row number of the maximum value in a partial column of a matrix. The partial column corresponds with the non-zero values of an equivalent lower ...
5
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1answer
79 views

Manually writing a function matrixpower() in R

Problem 1 - Matrix powers in R R does not have a built-in command for taking matrix powers. Write a function matrixpower() with two arguments mat and k ...
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1answer
51 views

A matrix-vector multiply parallelized using boost::MPI

This program performs a matrix-vector multiply using MPI to split the computation up. It is not extremely robust (for example, it doesn't handle the case where the number of MPI processes does not ...
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1answer
136 views

Matrix class with space-optimized triangular (lower and upper) variants

I've written a class for square numerical matrices (of doubles, in this case), in C++11. Since I intend to use this class later ...
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1answer
66 views

Transpose of a very large matrix with fewer than 1021 rows with Python

I have a matrix of fewer than 1021 rows. I'd like to take its transpose, but it is too big for GNU datamash and awk solutions to ...