# 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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### 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 ...
115 views

### Clockwise rotate a matrix in Scala

Given a matrix, clockwise rotate elements in it. Examples: ...
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### Print matrix in spiral order in Scala

Problem: Given a square or rectangular matrix, print its element in spiral order. For example, if input matrix is this: ...
146 views

I have written an implementation of the Strassen Vinograde Algorithm, but it's running slowly because of recursive creation of static arrays. I know that dynamic arrays would solve this problem, but I'...
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### SIMD product of a 4×4 matrix and a vector

I wrote a matrix class for use in a ray tracer. I already have a 'scalar' version up and running, but now I'm trying to rewrite it to use Intel SIMD Instrinsics. I realize my compiler (clang-7.0.0) ...
84 views

### Matrix arithmetic operations

I am currently attempting to implement Matrix Math for another project I am working on. However, I am not sure whether this implementation will work. Can someone please tell me if there are any ...
81 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....
76 views

### Finding valid path on 2D Grid

I got a 2D grid (n x n matrix). The user selects his player in this 2D grid and after that selects another node in this grid to mark his destination position. The player is allowed to move ...
106 views

### Template matrix class, second version

This is my first matrix class which I updated after already asking here already. The updated code is below. Are there any suggestions regarding member function parameters? Is there a convenient ...
31 views

### MinMax product for large matrices

I created this program which runs with no error, but I'd like to have some comments if it is possible to optimize it, since I need to run the program with N = 3200. ...
776 views

### Basic beginner's matrix class in Python

This is my first class. I've been working a while on it, some functions are future ideas and are right now just bare bones and intended to be worked on later. I'm really looking for a good review of ...
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### 2D Matrix with jagged array isn't faster than one with a multidimensional array

I was trying to use Math.Net's dense matrix class. But, it doesn't support int. So, I have to create a wrapper for a jagged 2d array. I knew that jagged arrays ...
60 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. ...
209 views

### Drawing concentric circles to console

This prints out a triple layer circle with 12 points per circle and finds the points across a grid. I had a really hard time with this and I'm planning to implement a lot more code but I don't want ...
171 views

### Find the longest line in 2D (MxM) array (vertical, horizontal, or diagonal)

Find the length of the longest line with given square (MxM) matrix. (vertical, horizontal, or diagonal allowed) (Length of the longest line = number of consecutive 1's) i.e.) input: ...
919 views

### Determinant using Gauss Elimination

We had a question in examination to compute determinant of general square matrix. Now I had made the normal program using Laplace Formula of determinant, ie, recursive solution. Now I was thinking of ...
7k views

### Python 3 function to rotate an image 90°

A coding challenge that rotates an image 90 degrees counterclockwise. The image is represented as an array matrix. I believe the time complexity is O(n2), but I'd like to know for sure, as well as any ...
85 views

### Custom matrix object in C++

I have been getting back into C++ today, after a few years of Python and R. I am completely rusty, but decided to create a matrix object to re-familiarise. In reality I wouldn't use this class, since ...
60 views

### Fast algorithm for any(M==2)

I want to find a quick way to see if a matrix M has at least one value that is, say, 2. In R, I would use any(M==2). However, this computes first ...
286 views

### Group-wise deviations from means / centering with dplyr vs. data.table

I am trying in R to "center" a matrix (i.e. remove mean) group-wise (i.e. remove group means for each variable). Input is a matrix (including the grouping variable), and output is the same matrix, ...
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### Creating the design matrices for a canonical correlation analysis

I have this code to generate symmetric matrices for testing how the design of the canonical correlation analysis I am performing works out. This is a extension of this solution Each row of the matrix ...
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### Combine Matrix Columns JavaScript

I did this Codepen to combine all the columns from one matrix in JS. ...
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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: ...
61 views

### Eigenvector calculation involving three matrices

Code performs well for small matrices, but gives memory error for large matrices of size 63000x93000, even when I am using server with memory of 64GB, space 100GB, swap 40GB. ...
87 views

### Dijkstra in JavaScript

I am writing the solution of Dijkstra's algorithm in JS. This is what has happened so far. I need to make it so that the choice of nodes is by recursion. Tell me how to do this better. ...
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### Simple implementation of nxn Dense Matrix in Java

So far this is what I have completed. Still working on these two methods boolean isIdentityMatrix(DenseMatrix matrix); boolean isInvertible(DenseMatrix matrix); Suggestions are appreciated. Thanks. ...
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### Extended matrix generation

I am extending a matrix with some calculated values. This code runs very slowly. Is there a way to vectorize this with slice and ...
207 views

### Determinant of a matrix of doubles

I have been working with some matrix functions and need the determinant. I have looked at several examples, but they all seem to use a hard coded size for the matrix, or calculate for a matrix of int, ...
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### CUDA kernel to compare matrix entries, weighted with a pattern

I wonder if it's possible to optimize this code in CUDA. Could I get any hints how to? Equivalent algorithm runs faster in Matlab for me, but there I'm doing matrix operations. Compution I'm not ...
118 views

### Demonstration of Find Vowel Square

Have the function VowelSquare(strArr) take the strArr parameter being passed which will be a 2D matrix of some arbitrary size filled with letters from the alphabet, and determine if a 2x2 square ...
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### Sum of diagonal elements in a matrix [closed]

The idea is to calculate sum of diagonals example [[1,2,3],[4,5,6],[7,8,9] the correct answer would be [1,5,9][3,5,7] = total 30 ...
77 views

### R Function to Generate Predictions from Ratings and Save Results

I am trying to generate predictions using the function below in combination with sapply. My actual datasets are very large, I am attempting to make 1.5 million predictions with this function and it is ...
484 views

### Codewars: N-dimensional Von Neumann Neighborhood in a matrix

Task: For creating this challenge on Codewars I need a very performant function that calculates Von Neumann Neighborhood in a N-dimensional array. This function will be called about 2000 times The ...
676 views

### MIPS Assembly Program to access elements in the 4x4 matrix, row or column-major oder

This MIPS Assembly program will make you access the elements in the 4x4 matrix in either row or column-major order i.e. accessing all elements row by row or column by column. Output is posted below ...
390 views

### A Simple Interactive Program that Can Solve A Linear System of Equations

So I was just reading my algebra-precalculus textbook, and learned that matrices can be used to solve systems of equations. Since the whole process seemed so algorithmic, I wondered if I could ...
997 views

### Print concentric rectangular patterns

I am solving interview questions from here. Problem : Print concentric rectangular pattern in a 2d matrix. The outermost rectangle is formed by A, then the next outermost is formed by A-1 and so on....
416 views

### Calculate median of a matrix

I am solving interview questions from here. Problem : Given a N cross M matrix in which each row is sorted, find the overall median of the matrix. Assume N*M is odd. Note: No extra memory is ...
156 views

### Math matrix, mainly for graphics

I wrote a matrix library to replace my old matrix library. I was using my old matrix library to do basic operations for 3D rendering but that library grew old and now I'm seeking to replace it. I'm ...
3k views

### Gaussian Elimination with Pivots

I'm pretty new to python, and coding in general. For practice, I've written the following code, which uses Gaussian reduction to solve a system of linear equations. ...
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### Class Matrix implementation

Following the 18.06 Linear algebra course, I was curious to reinvent the matrix class and basic functionality, like $PA=LU$ decomposition, Gauss elimination, finding inverse matrix etc. Any ...
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### Code to multiply matrices together

I've got a short algorithm used in my code to multiply two matrices and put them into a destination Matrix. I decided to use the temporary array t_elements, which ...