# tagged [matrix]

#### Convert a 1D array to a 2D array in numpy

Convert a 1D array to a 2D array in numpy I want to convert a 1-dimensional array into a 2-dimensional array by specifying the number of columns in the 2D array. Something that would work like this: D...

- Modified
- 18 Jul at 04:40

#### Inverse of a matrix using numpy

Inverse of a matrix using numpy I'd like to use numpy to calculate the inverse. But I'm getting an error: To calculate inverse of a matrix in numpy, say matrix M, it should be simply: `print M.I` Here...

#### Transposing a 2D-array in JavaScript

Transposing a 2D-array in JavaScript I've got an array of arrays, something like: I would like to transpose it to get the following array: It's not difficult to programmatically do so using loops: ```...

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- 18 Oct at 07:56

#### Vector of Vectors to create matrix

Vector of Vectors to create matrix I am trying to take in an input for the dimensions of a 2D matrix. And then use user input to fill in this matrix. The way I tried doing this is via vectors (vectors...

#### How to create an empty matrix in R?

How to create an empty matrix in R? I am new to R. I want to fill in an empty matrix with the results of my `for` loop using `cbind`. My question is, how can I eliminate the NAs in the first column of...

#### How do you rotate a two dimensional array?

How do you rotate a two dimensional array? Inspired by [Raymond Chen's post](https://devblogs.microsoft.com/oldnewthing/20080902-00/?p=21003), say you have a 4x4 two dimensional array, write a functio...

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- 22 Feb at 17:25

#### Is there any method for multiplying matrices having O(n) complexity?

Is there any method for multiplying matrices having O(n) complexity? I want to multiply two matrices but the triple loop has O(n) complexity. Is there any algorithm in dynamic programming to multiply ...

#### Recommendation for C# Matrix Library

Recommendation for C# Matrix Library I need a C# library to deal with matrices. It should implement singular value decomposition, matrix inversion, etc I've used [CSML](http://www.codeproject.com/Arti...

#### How to create fast and efficient filestream writes on large sparse files

How to create fast and efficient filestream writes on large sparse files I have an application that writes large files in multiple segments. I use FileStream.Seek to position each wirte. It appears th...

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- 23 Jul at 18:5

#### Difference between numpy dot() and Python 3.5+ matrix multiplication @

Difference between numpy dot() and Python 3.5+ matrix multiplication @ I recently moved to Python 3.5 and noticed the [new matrix multiplication operator (@)](https://docs.python.org/3/whatsnew/3.5.ht...

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- 7 Dec at 20:50

#### How to reshape an Array in c#

How to reshape an Array in c# I have a 3D array of bytes in c# which I have read from a bitmap: What is the easiest and more performance-friendly way of reshaping this array into 2D (linear) form? In ...

#### Create a basic matrix in C (input by user !)

Create a basic matrix in C (input by user !) I'm trying to ask the user to enter the number of columns and rows they want in a matrix, and then enter the values in the matrix... I'm going to let them ...

#### What does the error "arguments imply differing number of rows: x, y" mean?

What does the error "arguments imply differing number of rows: x, y" mean? I'm trying to create a plot from elements of csv file which looks like this: I tried the following code but am receiving an e...

#### Android: How to rotate a bitmap on a center point

Android: How to rotate a bitmap on a center point I've been looking for over a day for a solution to this problem but nothing helps, even the answers here. Documentation doesn't explain anything too. ...

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- 21 Aug at 15:17

#### How to properly mask a numpy 2D array?

How to properly mask a numpy 2D array? Say I have a two dimensional array of coordinates that looks something like `x = array([[1,2],[2,3],[3,4]])` Previously in my work so far, I generated a mask tha...

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- 5 Jul at 01:18

#### Why is there huge performance hit in 2048x2048 versus 2047x2047 array multiplication?

Why is there huge performance hit in 2048x2048 versus 2047x2047 array multiplication? I am making some matrix multiplication benchmarking, as previously mentioned in [Why is MATLAB so fast in matrix m...

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- 23 May at 10:34

#### Apply a function to every row of a matrix or a data frame

Apply a function to every row of a matrix or a data frame Suppose I have a n by 2 matrix and a function that takes a 2-vector as one of its arguments. I would like to apply the function to each row of...

#### How do I find the length (or dimensions, size) of a numpy matrix in python?

How do I find the length (or dimensions, size) of a numpy matrix in python? For a numpy matrix in python How can I find the length of a row (or column) of this matrix? Equivalently, how can I know the...

#### Generate an Adjacency Matrix for a Weighted Graph

Generate an Adjacency Matrix for a Weighted Graph I am trying to implement [Floyd-Warshall Algorithm](http://en.wikipedia.org/wiki/Floyd%E2%80%93Warshall_algorithm). To do this it requires me to set u...

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- 16 Jul at 23:23

#### Create dataframe from a matrix

Create dataframe from a matrix How to get a data frame with the same data as an already existing matrix has? A simplified example of my matrix: I would l

#### Boost Library, how to get determinant from lu_factorize()?

Boost Library, how to get determinant from lu_factorize()? I am trying to calculate a determinant using the boost c++ libraries. I found the code for the function InvertMatrix() which I have copied be...

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- 14 Sep at 04:30

#### How to implement decision matrix in c#

How to implement decision matrix in c# I need to make a decision based on a rather large set of 8 co-dependent conditions. Each of the conditions from A to H can be true

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- 3 Jun at 15:58

#### The compiler complains with "Error: stray '\240' in program"

The compiler complains with "Error: stray '\240' in program" It is wanted of me to implement the following function: Parameters a, r, c and f are input and b is output. “a” and “b” are two-dimensional...

#### How to write a confusion matrix

How to write a confusion matrix I wrote a confusion matrix calculation code in Python: ``` def conf_mat(prob_arr, input_arr): # confusion matrix conf_arr = [[0, 0], [0, 0]] for i in range(len(pr...

- Modified
- 12 Oct at 04:18