Which mldivide ('\') function is better
3 views (last 30 days)
Show older comments
Dear,
I have a 9x9 float matrix M, when I use it to \ function and got pretty much diferent result (P) between Matlab 2008 and 2015.
P = M \ eye(size(M))
My question is - Which one is better ? mldivide() in 2015 or mldivide() in 2008 Matlab version ? (suppose later is better ?)
Thanks,
--Dan
0 Comments
Accepted Answer
Bruno Luong
on 3 Dec 2018
Edited: Bruno Luong
on 3 Dec 2018
Use pseudo inverse PINV to get more stable solution. Never use "\" on nearly singular matrix. You are happy with 2008 is just pure luck.
0 Comments
More Answers (2)
the cyclist
on 29 Nov 2018
I highly doubt that a bug was found in mldivide later than 2008, so I doubt the later function is "more correct" or "more accurate". Instead, I suppose that there was some minor algorithmic change (e.g. some kind of time optimization).
How big is the difference between the two results? I'm guessing it is very small -- the order of normal floating point error -- such that the difference is down around the level of the overall accuracy of the calculation in the first place.
Can you upload the matrix M in a MAT file?
0 Comments
Dan NG
on 29 Nov 2018
3 Comments
Walter Roberson
on 29 Nov 2018
Differences that big suggest that either you are working with values near 1E-20 or else that your matrix is nearly singular.
See Also
Categories
Find more on Logical in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!