Thread: Matrix Class & more...

Here's the matrix header file

here's the vector header file

Here's an example usage for the matrix header...

Inverse? Would that make something like

1 2 3
4 5 6
7 8 9

into

9 8 7
6 5 4
3 2 1

?

If so, I could do it, but there's probably an easier way...

Code:

	for (x=0; x<10; x++)	//x is row, y is column
	{
		for (y=0; y<10; y++)
		{
			iMatrix1[x][y] = x*y;
		}
	}

	for (x=9,a=0; x>=0; x--,a++)	//a is row, b is column
	{
		for (y=9,b=0; y>=0; y--,b++)		//this loop is first loop flipped diagonally
		{
			iMatrix2[a][b] = x*y;
		}
	}

The first loop makes a matrix containing the multiplication table up to 9x9, the second reverses it like I mentioned before. You'd just have to change the x*y part

Yea, finding the inverse of a matrix isn't a trivial matter. If you want to do it the easiest, most general way, an augmented matrix like this is created:

a b c 1 0 0
d e f 0 1 0
g h i 0 0 1

then row operations are performed until the left side is the identity matrix. Whatever is on the right side is the inverse of the original matrix.

e.g.:

1 0 0 A B C
0 1 0 D E F
0 0 1 G H I

then
A B C
D E F
G H I
is the inverse of the original.

As for that book... well, it REALLY sucks. Its the book used in my programming class at my school, but I never look at it because it sucks so much ass, IMHO. The author explains things in a poor order and a lot of stuff is not clearly explained at all.

Originally posted by Sang-drax
I know how to invert matrices using pen and paper. I use someone else's code in C++ when I have to invert matrices in my programs.

I don't know what the most efficient algorithm would look like (perhaps a contest).

Yes, I applied the same exact method in my matrix class to calculate inverses. I have a function which performs forward elimination and one that performs backwards elimination. It works well, I think, but it's only benefits are for when you are calculating the inverse of an nxn sized matrix. Seperate algorithms based on the size of the matrix could be made for faster calculations.

I can post the code if anyone is interested, but its a bit clunky and uncommented...

Thats why I don't rely on the book so much. I try help files and doing it on my own a lot. I'm getting a lot better now.