Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fast Calculation of Calendar Time-, Age- and Duration Dependent Time at
  Risk in the Lexis Space   In epidemiology, the person-years method is broadly used to estimate the
incidence rates of health related events. This needs determination of time at
risk stratified by period, age and sometimes by duration of disease or
exposition. The article describes a fast method for calculating the time at
risk in two- or three-dimensional Lexis diagrams based on Siddon's algorithm.

33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int