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MATLAB: how to calculate the 'determinant' of a matrix N*N in MATLAB

Answer 1

+4 A:

You can define the matrix like so (semicolons can be used for line breaks)

A = [1 2 3; 4 5 6; 7 8 0]
A =
     1     2     3
     4     5     6
     7     8     0

Then you calculate the determinate by using DET

det(A)

ans =
           27

Jonas 2010-10-25 21:10:11

i want the steps to calculate this determinant OK?for exemple:the determinant of a diagonal matrix is:diagonal=diag(A);determinant = -prod(diagonal);

Fisherman 2010-10-25 21:16:07

@Fisherman: You're not asking how to calculate it *in Matlab*. You're asking about the algebra behind it. I'm not sure this is the correct forum for this.

Nathan Fellman 2010-10-25 21:18:52

So , would you PLZ give me the correct forum. THANKS a lot!

Fisherman 2010-10-25 21:21:54

@Fisherman: I don't quite understand what you need. If you want to know the determinant, then you can use the function `det`. If you want intermediate steps (i.e. L/U decomposition), you can look at the help to the function `det` I linked in my answer, where they describe the algorithm. Or you can check Wikipedia (http://en.wikipedia.org/wiki/Determinant) for many other ways for calculating the determinant.

Jonas 2010-10-25 21:24:18

@Fisherman: If you need to know anything about the algorithm that goes beyond the algorithm description in the Matlab help (look at the link to LU in there as well) and in Wikipedia, I suggest this site: http://math.stackexchange.com/

Jonas 2010-10-25 21:26:27

It's OK , thank you SO muchNow i find my answer that's it

Fisherman 2010-10-25 21:33:01

clc;clear all;A=input ('Give me the matrix A : ');[m,n]=size(A)for i = 2:1:mfor p = 1:1:i-1A(i,:)=A(i,:)-(A(i,p)/A(p,p))*A(p,:);diagonal=diag(A);determinant = -prod(diagonal);endend

Fisherman 2010-10-25 21:34:04

@Fisherman: Glad everything works now. Please consider accepting my answer if you found it useful.

Jonas 2010-10-25 21:52:07

Answer 2

+1 A:

A = [ 1 2 3 4;
      5 6 7 8;
      1 2 3 4;
      5 6 7 8];
det(A)

Scottie T 2010-10-25 21:10:27

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MATLAB: how to calculate the 'determinant' of a matrix N*N in MATLAB

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