Bluebit Software Support Forum / Technical Support and Help / Online Matrix Calculator

Maximum matrix size increased

Trifon — Tue, 08 May 2007 05:57:34 GMT

Hello all,

Today we have increased the maximum matrix size for the Online Matrix Calculator, to 30 rows by 30 columns.

Cholesky and transpose

Numsgil — Fri, 06 Nov 2009 18:12:28 GMT

Generally I really like this tool, especially being on the internet makes it very easy to test ideas quickly.

Two suggestions:

1. The Cholesky decomposition on the site sometimes fails for matrices which are rank deficient but do posses a triangular decomposition. If you go to the wikipedia article on Cholesky decomposition, it describes a form with a diagonal matrix in the center. If you do it that way (which is actually faster since it requires fewer square roots), and then take the square root of the diagonal matrix, you can always form a cholesky triangular matrix for all semi positive definite symmetric matrices.

2. There isn't an obvious way to take the transpose of a matrix that I see. I've been experimenting with a complete orthogonal decomposition algorithm which works by doing:

A = Q1 * R1
R1^T = Q2 * R2
R1 = R2^T * Q2^T

A = Q1 * R2^T * Q2^T

I've been testing various small matrices by hand using the calculator to see how the algorithm works with different ranks, shapes, etc. So I first QR decompose A, then QR decompose the transpose of the first R. But to be able to actually do that I need to transpose the copy+pasted triangular matrix. Right now I have to hand transpose it, which is a pain and error prone.

Also, while I'm on the subject it would be nice to be able to construct a householder transformation algebraically. So some way to add/subtract matrices, scale them, and do outer products on them.

Weird values for 11x11 matrix inverted

Kong Georg — Tue, 07 Jul 2009 07:55:43 GMT

Hello!

I have tried to invert the following matrix:

5405 1517 172 460 527 770 1032 563 182 182 4291
1517 1517 0 0 0 0 0 0 0 0 1016
172 0 172 0 0 0 0 0 0 0 145
460 0 0 460 0 0 0 0 0 0 421
527 0 0 0 527 0 0 0 0 0 464
770 0 0 0 0 770 0 0 0 0 589
1032 0 0 0 0 0 1032 0 0 0 881
563 0 0 0 0 0 0 563 0 0 461
182 0 0 0 0 0 0 0 182 0 158
182 0 0 0 0 0 0 0 0 182 156
4291 1016 145 421 464 589 881 461 158 156 4291

The result is really really strange, with large numbers which simply do not seem right. Also, as far as I can see, multiplying the inverse with the original does not yield the neat diagonal line of 1's I would expect.

Would you have any idea why that may be the case?

Kind regards,

Kong Georg

Re: online calculator

vikram — Mon, 10 Nov 2008 10:45:11 GMT

Hey there,

I was wondering if the online calculator is good for finding eigen values and eigen vectors for unsymmetric matrices.

Thanks in advance for the replies

trace - sum of eigenvalues

chrisnyc — Sat, 02 May 2009 19:27:11 GMT

I submitted a matrix which I will give below. The trace was given as zero, the eigenvalues, when I added them up, summed to 1. I thought they should sum to zero (the trace). Can you explain what's happening?

Here is matrix I entered:

0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 0 1 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0
1 1 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
1 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 1 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0
0 1 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 1 0 1 1 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 1 1 0 1 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0
0 0 1 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0
0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0

Illegal values for Invertible Matix

lionheart1983 — Wed, 29 Apr 2009 18:22:22 GMT

This is the matrix I'm speaking of:

1 1 5
1 2 7
2 -1 4

Your online calculator doesn't seem to understand that this is an invertible matrix, why is that?

Hello

lionheart1983 — Wed, 29 Apr 2009 03:28:45 GMT

I'm a big fan of online matrix calculator (I'm a computer sceince student and find it very helpful and convenient to operate so far).

May I make a suggestion?

Can you add Diagonalizable matrix calculations, such as finding P and D matrices for a given matrix A such that: P^(-1)AP=D

And D is the fitting diagonal matrix of A.

I also study Machine Learning course, and one of the things I like in this course is to calculate myself the operations on matrices (filled with probabilities values). This means that I don't like to use Matlab, which is installed in my college's labs. So, checking on my calculations, I love using your online matrix calculator.

Welcome

Trifon — Thu, 26 Apr 2007 04:44:33 GMT

Please post here your comments and suggestions for the Online Matrix Calculator or report any bugs you have found.

Flawed LU Calculator

LUsuggestion — Thu, 19 Feb 2009 09:55:15 GMT

Hello. I believe that the way your calculator parses input is giving a flawed result for LU decomposition. Tell me if I'm wrong, but I believe that LU decompositions are only possible on matrices that use only Type III elementary operations. Here is an example, I typed in:

A =

2 1 1
6 4 5
4 1 3

I believe your calculator parses that input and optimizes it to:

6 4 5
4 1 3
2 1 1

I believe this will cause a flawed result because you performed a Type I elementary operation by changing the rows. The U that your calculator returned was:

6.000 4.000 5.000 <---- Type I operation
0.000 -1.667 -0.333
0.000 0.000 -0.600

I did it by hand by only using Type III elementary operations and I got U to be:

2 1 1
0 1 2
0 0 3

I may be wrong, but if I'm correct, I hope this helps. Nice work altogether though!

Determinant Bug

Zytropic — Tue, 16 Sep 2008 02:56:25 GMT

If the following is entered:

1470 -1000 5

-1000 1950 -9

0 -270 9

The returned calculation is 14576400.

It should be 23346400.

Source code of Online Matrix Calculator

Trifon — Sat, 30 Jun 2007 03:58:16 GMT

The source code of the Oniline Matrix Calculator is freely available in the attachment of this post.

After downloading and un-zipping the source code on your web server you will need to complete the following steps:

Add the files Bluebit.MatrixLibrary.dll and Xheo.Licensing.dll in the /bin folder.
Place a previously activated single machine license in the /bin folder
Open and build the C# project.