Picking Generators of Homology

nukpezah@...
 

Hi
I have a question about picking generators of homology represented in the barcodes. I understand that the homology generators are equivalence classes of non boundary cycles, so we can only pick a representative. In Dionysus, the persistence_homology class gives us the reduced representation of the boundary matrix from which I presume we can read off the homology generators. But I am confused about how to do that. In my understanding, we have some ordering of the simplices in the filtration, hence the columns of reduced boundary matrices gives you the indexed simplices that give you the generators? But it does not tell you the actual collection of vertices that generate the indexed simplices in the reduced boundary matrix? I guess I am confused about this code on the site shown below; how do you read from this code that the simplex [o,1,2] is a homology generator for H1( one homology). Thanks
Jon
>>> m = d.homology_persistence(f)
 >>> for i,c in enumerate(m):
 ...     print(i, c)
 0
 1
 2 1*0 + 1*1
 3
 4 1*1 + 1*3
 5

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