error in inverting matrix

#1 Posted: 2/11/2010 3:28:00 PM

0 likes in 8 posts.

Group: User

hi

i was trying to invert a matrix with smath winxp 2010-feb10 version.
It gives me an error that "matrix is noninvertible (determinant equals zero)".
the determinant is not zero, i have checked. i have tried the M^-1 and invert(M) too. but gives the same error.

if i do this, then it works, calculates the result:
M:=...
M^-1= RESULT

if I do this, then it does not work:
M:=...
M2:=M^-1
M2= ERROR

#2 Posted: 2/11/2010 3:46:07 PM

buenos

0 likes in 8 posts.

Group: User

M=1/sqrt(2)*mat(1,-1,0,0,0,0,1,-1,1,1,0,0,0,0,1,1,4,4)
det(M)=-1 so it is not zero
if i change the matrix, to get a different determinant, not -1, then it wors.

#3 Posted: 2/11/2010 3:49:04 PM

Andrey Ivashov

2270 likes in 3734 posts.

Group: Super Administrator

Hello.

I can't reproduce this error with my matrices:

Could you please send your full example to support[at]smath[dot].info?

Best regards, Andrey Ivashov.

#4 Posted: 2/11/2010 3:53:19 PM

Andrey Ivashov

2270 likes in 3734 posts.

Group: Super Administrator

OK, I see now, thanks. Will check in 5 hrs.

#5 Posted: 2/11/2010 9:01:07 PM

Andrey Ivashov

2270 likes in 3734 posts.

Group: Super Administrator

Figured out that this error was in previous versions of SMath Studio as well when trying to evaluate symbolically:
[MATH](1/sqrt(2)*mat(1;-1;0;0;0;0;1;-1;1;1;0;0;0;0;1;1;4;4))^{-1}—#[/MATH]

Starting work to fix it.

#6 Posted: 2/11/2010 10:01:01 PM

buenos

0 likes in 8 posts.

Group: User

ok,
thanks.

#7 Posted: 2/15/2010 1:18:02 AM

Andrey Ivashov

2270 likes in 3734 posts.

Group: Super Administrator

Here is modified version of SyLib.dll file for SMath Studio 0.87 where this bug fixed: https://smath.com/files/Download/hkzMV (just unpack it and replace original SyLib.dll from Program Files/SMath/SMath Studio folder).
You can use it till next version of the program will be released.

Regards.

SMath Forum

error in inverting matrix - Messages