Matrix is singular

Question

I was tracing back processes and created a new process of electricity mix, I did not save any changes, however when I tried to calculate the previous version I got an error saying that the matrix is singular, what could I have done that creates such an error? Especially considering that I did not save changes.

I can not evaluate any process of ecoinvent and I have tried with different methods (EF, IPCC).

Answer 1

Hi, when you did not save anything then of course you will not get different results from before, but maybe you did some changes and saved them, before? 

A singular matrix (the message refers to the technosphere matrix) cannot be solved, simply speaking; you get this e.g. when you have rows or lines in the matrix that are linearly dependent from each other, so e.g. just a constant factor different. This happens e.g. if you have two lines that are completely 0. This is the inventory calculation, so using a different impact method does not help. 

You can check the matrix by enabling matrix image export in openLCA (go to preferences) and then you can, for a product system, export the matrices from the calculation. Check the A matrix.

Hope this helps, Andreas

Comments

Hi Andreas,
I have the same error regarding the singularity of the matrix.
I did what you advised but I am not sure what I should be looking for? There is no empty lines and it does not seem to be dependent ones as well.
Thank you for your help.
Anne

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It can also be non-epmty lines that are linearily dependent. We have a new version 2.2 (available in the developer owncloud folder) which should address these (or let's more cautiously say most of the) cases with a singular matrix. Maybe you can give it a try?