Please help me to calculate Inverese matrix that doesn't appear : warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 7.142796e-039.

Dear all,

I have a big problem of calculating the inverse matrix of matrix M0 (attached file).

Please help me out.

Thank you guys so much!

Answer 1

[Matz Johansson Bergström]

I'm not a numerical analysis expert, but if the matrix is "near singular", then the matrix is what is called "ill-conditioned" and it's determinant is very close to zero, so "all bets are off".

We can check how well it would invert:

cond(M0)

gives about

4e18

As a rule of thumb, a condition number of 10^k indicates that you will loose about k digits in precision, which in this case is very bad. See http://en.wikipedia.org/wiki/Condition_number.

This means that the matrix will introduce large errors when you do any kind of calculations with it, such as an inverse. I found this which might help you: http://www.mathworks.se/matlabcentral/newsreader/view_thread/67650 In the link, they mention the use of "psuedo inverse" pinv(), you should check it out.

[tuyen Nguyen]

Thank you so much for your answer,

I did try it by pinv, but when I check the result pinv(M0)*M0 is not equal to an unit matrix.