For positive integers,
r
â„
3,
h
â„
1, and
k
â„
1, BollobĂĄs, Saito, and Wormald proved some sufficient conditions for an
hâedgeâconnected
râregular graph to have a
kâfactor in 1985. Lu gave an upper bound for the third largest eigenvalue in a connected
râregular graph to have a
kâfactor in 2010. Gu found an upper bound for certain eigenvalues in an
hâedgeâconnected
râregular graph to have a
kâfactor in 2014. For positive integers
a
â€
b, an even (or odd)
[
a
,
b
]âfactor of a graph
G is a spanning subgraph
H such that for each vertex
v
â
V
(
G
),
d
H
(
v
) is even (or odd) and
a
â€
d
H
(
v
)
â€
b. In this paper, we prove upper bounds (in terms of
a
,
b
, and
r) for certain eigenvalues (in terms of
a
,
b
,
r
, and
h) in an
hâedgeâconnected
râregular graph
G to guarantee the existence of an even
[
a
,
b
]âfactor or an odd
[
a
,
b
]âfactor. This result extends the one of BollbĂĄs, Saito, and Wormald, the one of Lu, and the one of Gu.