Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Deciding Morality of Graphs is NP-complete   In order to find a causal explanation for data presented in the form of
covariance and concentration matrices it is necessary to decide if the graph
formed by such associations is a projection of a directed acyclic graph (dag).
We show that the general problem of deciding whether such a dag exists is
NP-complete.

16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio