## matrix

### LaTeX: How to add a matrix in a LaTeX document?

How to add a matrix in LaTeX? ...

### A Transpose/Unzip Function in Python

I have a list of 2-item tuples and I'd like to convert them to 2 lists where the first contains the first item in each tuple and the second list holds the second item. For example: original = [('a', 1), ('b', 2), ('c', 3), ('d', 4)] # and I want to become... result = (['a', 'b', 'c', 'd'], [1, 2, 3, 4]) Is there a builtin function th...

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

Inspired by Raymond Chen's post, say you have a 4x4 two dimensional array, write a function that rotates it 90 degrees. Raymond links to a solution in pseudo code, but I'd like to see some real world stuff.     Becomes:     Update: Nick'...

### int matrix with pointers in C - memory allocation confusion

Hello! I'm having some issues with producing an int matrix without creating memory leaks. I want to be able to make a given (global) matrix into any size dynamically via read_matrix(). But then i want to be able to free the memory later on. So in my main method the second printf should result in a bus error since it should not have any ...

### How do I get the current size of a matrix stack in OpenGL?

How do I get the current size of a matrix stack (GL_MODELVIEW, GL_PROJECTION, GL_TEXTURE) in OpenGL? I want this so that I can do some error checking to ensure that in certain parts of the code I can check that the matrix stacks have been left in the original condition. ...

### GPU programming on Xbox 360

I'm looking for some insight into XNA on Xbox 360, mainly if its possible to run vector-based float mathematics on its GPU? If there's a way, can you point me into the right direction? ...

### 3d to 2d Projection Matrix

I have 3 points in 3d space. I know the exact locations of them. Suppose they are (x0,y0,z0) (x1,y1,z1) (x2,y2,z2) Also i have a camera that are looking at these 3 points and i know the 2d locations of those three points on camera view plane. So for example (x0,y0,z0) will be (x0',y0') and (x1,y1,z1) will be (x1',y1') and (x2,y2,z2) wil...

### How can I sort a 2-D array in MATLAB with respect to one column?

I would like to sort a matrix according to a particular column. There is a sort function, but it sorts all columns independently. For example, if my matrix data is: 1 3 5 7 -1 4 Then the desired output (sorting by the first column) would be: -1 4 1 3 5 7 But the output of sort(data) is: -1 3 1 ...

### Is there a library for Linear algebra matrix handling in Java?

Is there any libraries in java that allow using mathematical matrices? I am looking for a library that allows me to perform operations in matrices such as invert, scalar multiplication, linear transformations, etc. etc. etc. In a nutshell, the operations required for lineal algebra. ...

### Invert 4x4 matrix - Numerical most stable solution needed.

I want to invert a 4x4 matrix. My numbers are stored in fixed-point format (1.15.16 to be exact). With floating-point arithmetic I usually just build the adjoint matrix and divide by the determinant (e.g. brute force the solution). That worked for me so far, but when dealing with fixed point numbers I get an unacceptable precision loss ...

### determining points from set of pairwise distances

given a matrix of distances between points is there an algorithm for determining a set of n-dimensional points that has these distances? (or at least minimises the error) sort of like a n-dimensional version of the turnpike problem. The best I can come up with is using multidimensional scaling. ...

### What is the easiest way to align the Z axis with a vector?

Given a point such as (0, 0, 0) and a vector like (x, y, z). What is the easiest way to align the negative Z-axis centered at (0, 0, 0) to point in the direction of this vector? Examples using OpenGL would be welcome, but not neccessary. ...

### Python Inverse of a Matrix

How do I get the inverse of a matrix in python? I've implemented it myself, but it's pure python, and I suspect there are faster modules out there to do it. ...

### MySource Matrix - Opinions

Has anyone had experience with MySource Matrix as a content management system? If so, thoughts/opinions/comments? Thanks in advance. ...

### Best way to represent a 2-D array in C++ with size determined at run time

In C++ I'd like to do something like: int n = get_int_from_user(); char* matrix = new char[n][n]; matrix = 'c'; //... matrix[n][n] = 'a'; delete [][] matrix; but of course this doesn't work. What is the best way to do something similar? I've seen some solutions to this but they seem pretty messy. ...

### Does anyone have any experience using math.net

I have a project on my plate that will involve a lot of linear algebra; mostly matrix and vector algebra. I've been looking for a library to help me out, and I came across math.net http://mathnet.opensourcedotnet.info/ Math.net I am doing this project in .net 3.5 and will be using C# Does anyone have any experience with this librar...

### How can I implement a RESTful webservice using C++?

Hi, I have to develop a computing intensive Web Service (say we are making really big Matrix computations) so I've think that the way to go is coding it in C++. I can't do a wrapper using SWIG or JNI in Java to benefit from the WS existing libraries because the computations are state dependant and involve big matrices. Passing those val...

### Database Bejewelled Puzzle- How does this solution work?

I'm interested in the programming challenge presented by the game Bejewelled. It seems like a simple game but programmatically it's more complex that it looks. In my search for hints on how the board is evaluated, I came across this QUIZ put on by the good folks at Simple-Talk. They have posted the winning answer, but I'm tarred and f...

### How can I calculate the inverse of a matrix?

Can somebody show me how to calculate the inverse of a matrix? I'm using VC++ 6.0 ...

### .Net Matrix

Is there a standard .Net matrix class? I cannot find it if there is. If not, why not? It sounds like something people would need very frequently. Are there any non-standard libs you could recommend? ...