Package: rvect
rvect.pyis a Python module that defines a class (Rvect) implementing a data type
that simulates the vector data type used in theRlanguage for statistical computing.Mathematical operations on vectors (Rvect objects) are similar in syntax but
different in function than operations on Python lists. In general, operations on
vectors are applied to each element of the vector, rather than to the vector as a
whole. Whereas multiplying a Python list by a positive integer extends the length
of the list, multiplying a vector by a positive integer increases the magnitude
of each element of the vector but does not change the length of the vector.Thervectmodule does not interact in any way withR–other Python modules
(e.g.,RPy) provide that functionality. Thervectmodule only provides another
Python data type, similar to vectors in R, that are useful for some types of
calculations.ExamplesTo illustrate the usage of Rvect objects, the following examples contrast operations
on Python lists and on Rvect objects.Multiplying by a scalar>>> [1, 2, 3] * 2
[1, 2, 3, 1, 2, 3]
>>> Rvect([1, 2, 3]) * 2
[2, 4, 6]Adding a scalar>>> [1, 2, 3] + 2
TypeError
>>> Rvect([1, 2, 3]) + 2
[3, 4, 5]Multiplying two lists or vectors>>> [1, 2, 3] * [4, 5, 6]
TypeError
>>> Rvect([1, 2, 3]) * Rvect([4, 5, 6])
[4, 10, 18]Adding two lists or vectors>>> [1, 2, 3] + [4, 5, 6]
[1, 2, 3, 4, 5, 6]
>>> Rvect([1, 2, 3]) + Rvect([4, 5, 6])
[5, 7, 9]Binary logical operations on two lists or vectors>>> [True, True, False, False] and [True, False, True, False]
[True, False, True, False]
>>> list_and( [True, True, False, False], [True, False, True, False] )
[True, False, False, False]
>>> Rvect([True, True, False, False]).logical_and( Rvect([True, False, True, False]) )
[True, False, False, False]NotesThis module contains several functions that implement basic listwise operations
(e.g., and, or, sum, product) on lists or tuples, in addition to the class (Rvect)
that defines overloaded operators for these and other functions.Whereas elements of an R vector must all be of the same type, the Rvect class has
no such constraint–Rvect elements may be of any type, as with a Python list. The
class does contain methods to coerce all elements to several specific types, however.Because Python does not allow a class to define its own __not__ method, the commandnot Rvect()does not work as might be expected (that is, not as in R). Instead, there is a method named.logical_not()of an Rvect object that must be called instead.Because Python implements the logical binary infix operations ‘and’, ‘or’, and ‘xor’
by calling __nonzero__ or __len__ on each object and then executing the Boolean logic
itself, logical binary combination of Rvect objects cannot be done using the ‘and’,
‘or’, and ‘xor’ infix operators. Instead, the following functions are defined.logical_and(Rvect1, Rvect2, ...)
.logical_or(Rvect1, Rvect2, ...)
.logical_xor(...)The special methods __and__, __or__, and __xor__, which correspond to the binary
infix operators ‘&’, ‘|’, and ‘^’,are for binary, not logical, comparisons. In R,
however, these infix operators peform logical comparisons. Therefore, the special
methods have been implemented so that they convert their arguments to booleans, and
therefore correspond to logical operators, and so operate similarly to the equivalent
R operators. Thus, for Rvects a and b, the following two expressions are equivalenta.logical_and(b) a & bBoth return a vector of booleans. As per the previous note, these arenotequivalent toa and bwhich returns a single boolean value.The'list_...()'functions in this module allow operation on multiple lists, whereas
the binary infix mathematical operators implemented for Rvect instances only allow
operation on two objects. For example, multiple lists can be summed in parallel withlist_sum(list1, list2, list3,...)However, the arguments to the'list_...()'functions must all be lists of the same
length, whereas the arguments to the Rvect methods may be other Rvect objects, lists,
or scalars.