How does a matrix indicate a point?

In summary, the Birkhoff-von Neumann polytope has vertices represented by permutation matrices, which are points in ℝN2 space. A 2x2 matrix with four elements maps to R4 and is represented by points in 4-space. The entries of the matrix can be read off in any order as long as it is consistent.
  • #1
mynameinc
9
0
I've been looking at the Birkhoff-von Neumann polytope, and the book stated that the vertices are given by the permutation matrices. So, can someone explain how matrices indicate a point in space?

Thanks,

mynameinc
 
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  • #2
The vertices are points in ℝN2 space.
 
  • #3
D H said:
The vertices are points in ℝN2 space.

I still don't understand. It says that (1 0//0 1), (0 1//1 0) are elements of B_2. How do those indicate points?

If you can't tell, I have several "For Dummies" books. :)
 
Last edited:
  • #4
A 2x2 matrix has four elements, in this case, four real numbers. That maps to R4, so they are represented by points in 4-space.
 
  • #5
D H said:
A 2x2 matrix has four elements, in this case, four real numbers. That maps to R4, so they are represented by points in 4-space.

So, does this map as (1,0,1,0) and (0,1,0,1)?

Also, thanks for the help.
 
  • #6
Usually if you have a matrix you just read it off from left to right, top to bottom. So the matrix

1 0
0 1

would be (1,0,0,1) and the matrix

0 1
1 0

would be (0,1,1,0). Of course it doesn't matter which order you put the entries of your matrix as long as you're consistent the whole time
 
  • #7
Office_Shredder said:
Usually if you have a matrix you just read it off from left to right, top to bottom. So the matrix

1 0
0 1

would be (1,0,0,1) and the matrix

0 1
1 0

would be (0,1,1,0). Of course it doesn't matter which order you put the entries of your matrix as long as you're consistent the whole time

Those are the coordinates I meant to give, lol.

Thanks for the help DH and Office Shredder. Now that I understand, do I need to place [SOLVED] or anything in the title line?
 

1. How does a matrix indicate a point?

A matrix indicates a point by using its rows and columns to represent the coordinates of the point. The first row corresponds to the x-coordinate, the second row corresponds to the y-coordinate, and the third row corresponds to the z-coordinate. The numbers in each column represent the magnitude and direction of each coordinate.

2. What is the purpose of using a matrix to indicate a point?

Using a matrix to indicate a point allows for mathematical operations, such as translation, rotation, and scaling, to be applied to the point. This makes it easier to manipulate and transform points in a 3D space.

3. Can a matrix indicate a point in a 2D space?

Yes, a matrix can indicate a point in a 2D space by using a 3x3 matrix with the third row and column being set to 0 and 1 respectively. This essentially ignores the z-coordinate and allows for points to be represented in a 2D space.

4. How is a matrix used to indicate multiple points?

A matrix can be used to indicate multiple points by creating a larger matrix with each column representing the coordinates of a different point. This allows for multiple points to be transformed simultaneously using the same matrix.

5. What is the relationship between a matrix and a point in a 3D space?

A matrix and a point in a 3D space are closely related as the matrix provides a way to represent and manipulate the point's coordinates. The matrix essentially acts as a transformation that can be applied to the point to change its position, orientation, or size in the 3D space.

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