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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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Converting Data in Rows and Columns to Rows in VBA for Excel

I have a working VBA script for Excel that converts a matrix of data with multiple records in per row to multiple rows with one record per row. A StackOverflow user told me that the code could use ...
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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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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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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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Creation of matrix with specific attempts at the end

What I want to do is build a Slay-the-Spire-like Map. As you can see in the following image, the map is splitted in ISteps and ...
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1answer
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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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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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Matlab: Matrix with negative numbers [closed]

I have a matrix, A = [745 x 678], which consists of negative and positive values. I would like to make all the negative numbers zero but am not sure how to go about doing this. I was thinking of ...
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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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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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3answers
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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
38 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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Rotate an N × N matrix 90 degrees clockwise

Given the problem from "Cracking the coding interview" Given an image represented by an NxN matrix, where each pixel in the image is 4 bytes, write a method to rotate the image by 90 degrees ...
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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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4x4 matrix implementation in C++

I've been doing some 3D graphics in OpenGL lately and I needed a way to work with 4x4 matrices. My implementation supports the following operations: Matrix-matrix addition. Matrix-matrix subtraction. ...
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1answer
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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
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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
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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...
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1answer
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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
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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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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. ...
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1answer
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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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1answer
135 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 ...
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1answer
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Extract numerics from matrix A with logical matrix B

I have a matrix A containing numeric values and a matrix B containing 0/1s: ...
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1answer
75 views

Applying a function to each row of a matrix

My goal is to apply a function func1 to each row of the matrix input and then return a new one resulting from the transformation....
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1answer
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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
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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
59 views

Applying a function to columns of two matrices producing their combinations

I made a short snippet for applying a function f that takes two arguments (vectors) to columns of two matrices producing all possible combinations of those columns. ...
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1answer
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Computing a Discrete Cosine Transform matrix

I'm learning Haskell and I needed to work with discrete cosine transform matrices, so I made a program that generates text (usable in WolframAlpha) containing the generated matrix. The elements of ...
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1answer
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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 ...
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1answer
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Calculating the potential of a matrix of size (424600, 55)

I have the following working code to calculate the potential of a matrix after normalizing the matrix. But it is too much time consuming. Is there a way to make this code run faster? ...
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Reading sparse matrix from binary file

I have binary files containing sparse matrices. Their format is: number of rows int length of a row int column index int value float Reading ...
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2answers
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JavaScript Spiral Matrix Coding Challenge

A whiteboarding challenge: Given a 2D array (matrix) inputMatrix of integers, create a function spiralCopy that copies ...
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1answer
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Decomposing a matrix as a sum of two bitstrings

I chanced upon this question and came up with the following algorithm, looking for criticisms and advice on how to improve my algorithm efficiency. You are given 3 arguments: A & B are ...
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2answers
106 views

Perturbed phase oscillator integration

I am integrating a system of perturbed phase oscillators. I define the system of equation and also the Jacobian matrix. I have to reshape the one dimensional vector of system state to a 2 dimensional ...
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1answer
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C++ Dataset class

C++ newbie trying to build a class to represent a dataset for the purposes of building predictive models of the form y ~ x0, x1,... Since this is version 1, I'm assuming some nice properties about my ...
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1answer
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Lambda based matrix

I am calling matrix implemented with a lambda "lambda matrix". The full working program: ...
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1answer
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Faster solution for row-wise matrix subtraction

I have 2 matrices. I have to calculate the euclidean distance between every row of matrix A and every row of matrix B. In the first solution I loop over the rows of the two matrices and for each row ...
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1answer
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Matrix multiplication using functions in C

This exercise surprised me a little bit. I did not expect that gcc (GCC 6.3.0 in the MinGW suite) would use the C11 standard by default, which I realised after I ...
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3answers
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JavaScript solution for diagonal difference

hackerrank.com - diagonal difference: Problem Statement You are given a square matrix of size N×N. Calculate the absolute difference of the sums across the two main diagonals. Input ...
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1answer
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Cache-optimized matrix multiplication algorithm in C

I am trying to optimize matrix multiplication on a single processor by optimizing cache use. I am implemented a block multiplication and used some loop unrolling, but I'm at a loss on how to optimize ...
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1answer
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Inverse mapping with bilinear interpolation on an image

The following is my solution for an inverse mapping with bilinear interpolation on an image. The original image is img and ...
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Calculate huge Fibonacci Numbers in C++ using GMP and boost::multiprecision

Problem Statement Calculate the exact value of the n-th Fibonacci number, say the one-billionth. Algorithm The algorithm is based on the idea that Fibonacci numbers can be represented as 2x2 ...
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1answer
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Minimum steps to reach target by a Knight In Scala

Given a chessboard of N size (square matrix), the position of Knight and position of a target, find out minimum steps (both count and exact steps) from start to target for a Knight. If it is not ...
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About the problem of seeking matrix inverse

Recently I have solved the inverse matrix in three ways, found that their work efficiency has obvious differences. This is the case: ...
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2answers
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Pandas calculations per columns and per rows for very big datasets

I am using a panda's dataframe and I am doing filtering and some calculations per column and per row. The dataframe looks this: ...
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2answers
109 views

Simple matrix library in C++

Today I started learning C++ and at the end of the day have made a simple generic matrix class. I'm looking for feedback on techniques and features. It's still not complete, though. But everything ...
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1answer
110 views

Multiplying two arrays

I would like to ask how I can make my code more simple and effective. I know that this code can be 100% better. I am supposed to load number for each array and then take the 2 arrays (4*3 and 3*4) and ...
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1answer
57 views

Blurring a given image using moving average in Python 3

I've tried solving the following HackerRank question: Write a function blur_image() that takes as a parameter an image in the form of a nested list ...
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2answers
171 views

Multiplication of 3×3 and N×N square matrices

I recently wrote a matrix module in C++. During the development process I quoted some source code and found a problem. For example, matrix multiplication: This way is suitable for all N×N matrices: ...