If either lowDegree or highDegree is not given, then they are inferred from the Betti diagram itself. The result matrix has highDegree-lowDegree+1 rows, corresponding to these (slanted) degrees.
B = pureBettiDiagram {0,1,4,7} |
matrix B |
matrix(B,-2) |
matrix(B,-2,5) |
This function is essentially the inverse of
mat2betti.
R = ZZ/101[a..e]; |
I = ideal borel monomialIdeal"abc,ad3,e4"; |
B = betti res I |
C = matrix B |
B == mat2betti C |
If the lowest degree of the matrix is not 0, then this information must be supplied in order to obtain the inverse operation.
B = pureBettiDiagram {-2,0,1,2,5} |
C = matrix B |
mat2betti(C,-2) |