equals.RdCompares an object with another and returns TRUE if they are equal.
The equal property must be
1) reflexive, i.e. equals(o1,o1) should be TRUE.
2) symmetric, i.e. equals(o1,o2) is TRUE if and only
if equals(o2,o1) is TRUE.
3) transitive, i.e. equals(o1,o2) is TRUE and
equals(o2,o3) is TRUE, then equals(o1,o3) should
be TRUE.
5) consistent, i.e. equals(o1,o2) should return the same
result on multiple invocations as long as nothing has changed.
6) equals(o1,NULL) should return FALSE, unless
o1 is also NULL.
By default identical() is used.
# Default S3 method
equals(object, other, ...)identical().