Elements of free modules

AUTHORS:

  • William Stein
  • Josh Kantor

TODO: Change to use a get_unsafe / set_unsafe, etc., structure exactly like with matrices, since we’ll have to define a bunch of special purpose implementations of vectors easily and systematically.

EXAMPLES: We create a vector space over \QQ and a subspace of this space.

sage: V = QQ^5
sage: W = V.span([V.1, V.2])

Arithmetic operations always return something in the ambient space, since there is a canonical map from W to V but not from V to W.

sage: parent(W.0 + V.1)
Vector space of dimension 5 over Rational Field
sage: parent(V.1 + W.0)
Vector space of dimension 5 over Rational Field
sage: W.0 + V.1
(0, 2, 0, 0, 0)
sage: W.0 - V.0
(-1, 1, 0, 0, 0)

Next we define modules over \ZZ and a finite field.

sage: K = ZZ^5
sage: M = GF(7)^5

Arithmetic between the \QQ and \ZZ modules is defined, and the result is always over \QQ, since there is a canonical coercion map to \QQ.

sage: K.0 + V.1
(1, 1, 0, 0, 0)
sage: parent(K.0 + V.1)
Vector space of dimension 5 over Rational Field

Since there is no canonical coercion map to the finite field from \QQ the following arithmetic is not defined:

sage: V.0 + M.0
Traceback (most recent call last):
...
TypeError: unsupported operand parent(s) for '+': 'Vector space of dimension 5 over Rational Field' and 'Vector space of dimension 5 over Finite Field of size 7'

However, there is a map from \ZZ to the finite field, so the following is defined, and the result is in the finite field.

sage: w = K.0 + M.0; w
(2, 0, 0, 0, 0)
sage: parent(w)
Vector space of dimension 5 over Finite Field of size 7
sage: parent(M.0 + K.0)
Vector space of dimension 5 over Finite Field of size 7

Matrix vector multiply:

sage: MS = MatrixSpace(QQ,3)
sage: A = MS([0,1,0,1,0,0,0,0,1])
sage: V = QQ^3
sage: v = V([1,2,3])
sage: v * A
(2, 1, 3)

TESTS:

sage: D = 46341
sage: u = 7
sage: R = Integers(D)
sage: p = matrix(R,[[84, 97, 55, 58, 51]])
sage: 2*p.row(0)
(168, 194, 110, 116, 102)
class sage.modules.free_module_element.FreeModuleElement

Bases: sage.structure.element.Vector

An element of a generic free module.

Mod(p)

EXAMPLES:

sage: V = vector(ZZ, [5, 9, 13, 15])
sage: V.Mod(7)
(5, 2, 6, 1)
sage: parent(V.Mod(7))
Vector space of dimension 4 over Ring of integers modulo 7
additive_order()

Return the additive order of self.

EXAMPLES:

sage: v = vector(Integers(4), [1,2])
sage: v.additive_order()
4
sage: v = vector([1,2,3])
sage: v.additive_order()
+Infinity
sage: v = vector(Integers(30), [6, 15]); v
(6, 15)
sage: v.additive_order()
10
sage: 10*v
(0, 0)
apply_map(phi, R=None, sparse=None)

Apply the given map phi (an arbitrary Python function or callable object) to this free module element. If R is not given, automatically determine the base ring of the resulting element.

INPUT:
sparse – True or False will control whether the result
is sparse. By default, the result is sparse iff self is sparse.
  • phi - arbitrary Python function or callable object
  • R - (optional) ring

OUTPUT: a free module element over R

EXAMPLES:

sage: m = vector([1,x,sin(x+1)])
sage: m.apply_map(lambda x: x^2)
(1, x^2, sin(x + 1)^2)
sage: m.apply_map(sin)
(sin(1), sin(x), sin(sin(x + 1)))
sage: m = vector(ZZ, 9, range(9)) 
sage: k.<a> = GF(9) 
sage: m.apply_map(k)
(0, 1, 2, 0, 1, 2, 0, 1, 2)

In this example, we explicitly specify the codomain.

sage: s = GF(3)
sage: f = lambda x: s(x)
sage: n = m.apply_map(f, k); n
(0, 1, 2, 0, 1, 2, 0, 1, 2)
sage: n.parent()
Vector space of dimension 9 over Finite Field in a of size 3^2

If your map sends 0 to a non-zero value, then your resulting vector is not mathematically sparse:

sage: v = vector([0] * 6 + [1], sparse=True); v
(0, 0, 0, 0, 0, 0, 1)
sage: v2 = v.apply_map(lambda x: x+1); v2
(1, 1, 1, 1, 1, 1, 2)

but it’s still represented with a sparse data type:

sage: parent(v2)
Ambient sparse free module of rank 7 over the principal ideal domain Integer Ring

This data type is inefficient for dense vectors, so you may want to specify sparse=False:

sage: v2 = v.apply_map(lambda x: x+1, sparse=False); v2
(1, 1, 1, 1, 1, 1, 2)
sage: parent(v2)
Ambient free module of rank 7 over the principal ideal domain Integer Ring

Or if you have a map that will result in mostly zeroes, you may want to specify sparse=True:

sage: v = vector(srange(10))
sage: v2 = v.apply_map(lambda x: 0 if x else 1, sparse=True); v2
(1, 0, 0, 0, 0, 0, 0, 0, 0, 0)
sage: parent(v2)
Ambient sparse free module of rank 10 over the principal ideal domain Integer Ring

TESTS:

sage: m = vector(SR,[])
sage: m.apply_map(lambda x: x*x) == m
True

Check that we don’t unnecessarily apply phi to 0 in the sparse case:

sage: m = vector(ZZ, range(1, 4), sparse=True)
sage: m.apply_map(lambda x: 1/x)
(1, 1/2, 1/3)

sage: parent(vector(RDF, (), sparse=True).apply_map(lambda x: x, sparse=True))
Sparse vector space of dimension 0 over Real Double Field
sage: parent(vector(RDF, (), sparse=True).apply_map(lambda x: x, sparse=False))
Vector space of dimension 0 over Real Double Field
sage: parent(vector(RDF, (), sparse=False).apply_map(lambda x: x, sparse=True))
Sparse vector space of dimension 0 over Real Double Field
sage: parent(vector(RDF, (), sparse=False).apply_map(lambda x: x, sparse=False))
Vector space of dimension 0 over Real Double Field
change_ring(R)

Change the base ring of this vector, by coercing each element of this vector into R.

EXAMPLES:

sage: v = vector(QQ['x,y'], [1..5]); v.change_ring(GF(3))
(1, 2, 0, 1, 2)
cross_product(right)

Return the cross product of self and right, which is only defined for vectors of length 3.

This product is performed under the assumption that the basis vectors are orthonormal.

EXAMPLES:

sage: v = vector([1,2,3]); w = vector([0,5,-9])
sage: v.cross_product(v)
(0, 0, 0)
sage: u = v.cross_product(w); u
(-33, 9, 5)
sage: u.dot_product(v)
0
sage: u.dot_product(w)
0
degree()
denominator()
dense_vector()
derivative(*args)

Derivative with respect to variables supplied in args.

Multiple variables and iteration counts may be supplied; see documentation for the global derivative() function for more details.

diff() is an alias of this function.

EXAMPLES:

sage: v = vector([1,x,x^2])
sage: v.derivative(x)
(0, 1, 2*x)
sage: type(v.derivative(x)) == type(v)
True
sage: v = vector([1,x,x^2], sparse=True)
sage: v.derivative(x)
(0, 1, 2*x)
sage: type(v.derivative(x)) == type(v)
True
sage: v.derivative(x,x)
(0, 0, 2)
dict(copy=True)
diff(*args)

Derivative with respect to variables supplied in args.

Multiple variables and iteration counts may be supplied; see documentation for the global derivative() function for more details.

diff() is an alias of this function.

EXAMPLES:

sage: v = vector([1,x,x^2])
sage: v.derivative(x)
(0, 1, 2*x)
sage: type(v.derivative(x)) == type(v)
True
sage: v = vector([1,x,x^2], sparse=True)
sage: v.derivative(x)
(0, 1, 2*x)
sage: type(v.derivative(x)) == type(v)
True
sage: v.derivative(x,x)
(0, 0, 2)
dot_product(right)

Return the dot product of self and right, which is the sum of the product of the corresponding entries.

INPUT:

  • right - vector of the same degree as self. It need not be in the same vector space as self, as long as the coefficients can be multiplied.

EXAMPLES:

sage: V = FreeModule(ZZ, 3)
sage: v = V([1,2,3])
sage: w = V([4,5,6])
sage: v.dot_product(w)
32
sage: W = VectorSpace(GF(3),3)
sage: w = W([0,1,2])
sage: w.dot_product(v)
2
sage: w.dot_product(v).parent()
Finite Field of size 3

Implicit coercion is well defined (regardless of order), so we get 2 even if we do the dot product in the other order.

sage: v.dot_product(w)  
2
element()
get(i)
get is meant to be more efficient than getitem, because it does not do any error checking.
inner_product(right)

Returns the inner product of self and other, with respect to the inner product defined on the parent of self.

EXAMPLES:

sage: I = matrix(ZZ,3,[2,0,-1,0,2,0,-1,0,6])
sage: M = FreeModule(ZZ, 3, inner_product_matrix = I)
sage: (M.0).inner_product(M.0)
2
sage: K = M.span_of_basis([[0/2,-1/2,-1/2], [0,1/2,-1/2],[2,0,0]])
sage: (K.0).inner_product(K.0)
2
integral(*args, **kwds)

Returns a symbolic integral of the vector, component-wise.

integrate() is an alias of the function.

EXAMPLES:

sage: t=var('t')                      
sage: r=vector([t,t^2,sin(t)])
sage: r.integral(t)
(1/2*t^2, 1/3*t^3, -cos(t))
sage: integrate(r,t)
(1/2*t^2, 1/3*t^3, -cos(t))
sage: r.integrate(t,0,1)
(1/2, 1/3, -cos(1) + 1)
integrate(*args, **kwds)

Returns a symbolic integral of the vector, component-wise.

integrate() is an alias of the function.

EXAMPLES:

sage: t=var('t')                      
sage: r=vector([t,t^2,sin(t)])
sage: r.integral(t)
(1/2*t^2, 1/3*t^3, -cos(t))
sage: integrate(r,t)
(1/2*t^2, 1/3*t^3, -cos(t))
sage: r.integrate(t,0,1)
(1/2, 1/3, -cos(1) + 1)
is_dense()
is_immutable()

Return True if this vector is immutable, i.e., the entries cannot be changed.

EXAMPLES:

sage: v = vector(QQ['x,y'], [1..5]); v.is_immutable()
False
sage: v.set_immutable()
sage: v.is_immutable()
True
is_mutable()

Return True if this vector is mutable, i.e., the entries can be changed.

EXAMPLES:

sage: v = vector(QQ['x,y'], [1..5]); v.is_mutable()
True
sage: v.set_immutable()
sage: v.is_mutable()
False
is_sparse()
is_vector()
iteritems()
lift()

EXAMPLES:

sage: V = vector(Integers(7), [5, 9, 13, 15]) ; V
(5, 2, 6, 1)
sage: V.lift()
(5, 2, 6, 1)
sage: parent(V.lift())
Ambient free module of rank 4 over the principal ideal domain Integer Ring
list(copy=True)
list_from_positions(positions)
nintegral(*args, **kwds)

Returns a numeric integral of the vector, component-wise, and the result of the nintegral command on each component of the input.

nintegrate() is an alias of the function.

EXAMPLES:

sage: t=var('t')                      
sage: r=vector([t,t^2,sin(t)])
sage: vec,answers=r.nintegral(t,0,1)
sage: vec
(0.5, 0.333333333333, 0.459697694132)
sage: type(vec)
<type 'sage.modules.vector_real_double_dense.Vector_real_double_dense'>
sage: answers
[(0.5, 5.5511151231257843e-15, 21, 0),
(0.33333333333333343, 3.7007434154171903e-15, 21, 0),
(0.45969769413186018, 5.1036696439228408e-15, 21, 0)]

sage: r=vector([t,0,1], sparse=True)
sage: r.nintegral(t,0,1)            
((0.5, 0.0, 1.0),
{0: (0.5, 5.5511151231257843e-15, 21, 0),
2: (1.0, 1.110223024625157e-14, 21, 0)})
nintegrate(*args, **kwds)

Returns a numeric integral of the vector, component-wise, and the result of the nintegral command on each component of the input.

nintegrate() is an alias of the function.

EXAMPLES:

sage: t=var('t')                      
sage: r=vector([t,t^2,sin(t)])
sage: vec,answers=r.nintegral(t,0,1)
sage: vec
(0.5, 0.333333333333, 0.459697694132)
sage: type(vec)
<type 'sage.modules.vector_real_double_dense.Vector_real_double_dense'>
sage: answers
[(0.5, 5.5511151231257843e-15, 21, 0),
(0.33333333333333343, 3.7007434154171903e-15, 21, 0),
(0.45969769413186018, 5.1036696439228408e-15, 21, 0)]

sage: r=vector([t,0,1], sparse=True)
sage: r.nintegral(t,0,1)            
((0.5, 0.0, 1.0),
{0: (0.5, 5.5511151231257843e-15, 21, 0),
2: (1.0, 1.110223024625157e-14, 21, 0)})
nonzero_positions()
Return the sorted list of integers i such that self[i] != 0.
norm(p='sage.rings.integer.Integer(2)')

Return the p-norm of this vector, where p can be a real number \geq 1, Infinity, or a symbolic expression. If p=2 (default), this is the usual Euclidean norm; if p=Infinity, this is the maximum norm; if p=1, this is the taxicab (Manhattan) norm.

EXAMPLES:

sage: v = vector([1,2,-3])
sage: v.norm(5)
276^(1/5)

The default is the usual Euclidean norm:

sage: v.norm()  
sqrt(14)
sage: v.norm(2)
sqrt(14)

The infinity norm is the maximum size of any entry:

sage: v.norm(Infinity)
3

Any real or symbolic value works:

sage: v=vector(RDF,[1,2,3])
sage: v.norm(5)
3.07738488539
sage: v.norm(pi/2)
4.2165958647
sage: _=var('a b c d p'); v=vector([a, b, c, d])
sage: v.norm(p)
(abs(a)^p + abs(b)^p + abs(c)^p + abs(d)^p)^(1/p)
normalize()

Return this vector divided through by the first nonzero entry of this vector.

EXAMPLES:

sage: v = vector(QQ,[0,4/3,5,1,2])
sage: v.normalize()
(0, 1, 15/4, 3/4, 3/2)
pairwise_product(right)

Return the pairwise product of self and right, which is a vector of the products of the corresponding entries.

INPUT:

  • right - vector of the same degree as self. It need not be in the same vector space as self, as long as the coefficients can be multiplied.

EXAMPLES:

sage: V = FreeModule(ZZ, 3)
sage: v = V([1,2,3])
sage: w = V([4,5,6])
sage: v.pairwise_product(w)
(4, 10, 18)
sage: sum(v.pairwise_product(w)) == v.dot_product(w)
True
sage: W = VectorSpace(GF(3),3)
sage: w = W([0,1,2])
sage: w.pairwise_product(v)
(0, 2, 0)
sage: w.pairwise_product(v).parent()
Vector space of dimension 3 over Finite Field of size 3

Implicit coercion is well defined (regardless of order), so we get 2 even if we do the dot product in the other order.

sage: v.pairwise_product(w).parent()  
Vector space of dimension 3 over Finite Field of size 3

TESTS:

sage: x, y = var('x, y') 
sage: parent(vector(ZZ,[1,2]).pairwise_product(vector(ZZ,[1,2]))) 
Ambient free module of rank 2 over the principal ideal domain Integer Ring 
sage: parent(vector(ZZ,[1,2]).pairwise_product(vector(QQ,[1,2]))) 
Vector space of dimension 2 over Rational Field 
sage: parent(vector(QQ,[1,2]).pairwise_product(vector(ZZ,[1,2]))) 
Vector space of dimension 2 over Rational Field 
sage: parent(vector(QQ,[1,2]).pairwise_product(vector(QQ,[1,2]))) 
Vector space of dimension 2 over Rational Field 
sage: parent(vector(QQ,[1,2,3,4]).pairwise_product(vector(ZZ[x],[1,2,3,4]))) 
Ambient free module of rank 4 over the principal ideal domain Univariate Polynomial Ring in x over Rational Field 
sage: parent(vector(ZZ[x],[1,2,3,4]).pairwise_product(vector(QQ,[1,2,3,4]))) 
Ambient free module of rank 4 over the principal ideal domain Univariate Polynomial Ring in x over Rational Field 
sage: parent(vector(QQ,[1,2,3,4]).pairwise_product(vector(ZZ[x][y],[1,2,3,4]))) 
Ambient free module of rank 4 over the integral domain Univariate Polynomial Ring in y over Univariate Polynomial Ring in x over Rational Field 
sage: parent(vector(ZZ[x][y],[1,2,3,4]).pairwise_product(vector(QQ,[1,2,3,4]))) 
Ambient free module of rank 4 over the integral domain Univariate Polynomial Ring in y over Univariate Polynomial Ring in x over Rational Field 
sage: parent(vector(QQ[x],[1,2,3,4]).pairwise_product(vector(ZZ[x][y],[1,2,3,4]))) 
Ambient free module of rank 4 over the integral domain Univariate Polynomial Ring in y over Univariate Polynomial Ring in x over Rational Field 
sage: parent(vector(ZZ[x][y],[1,2,3,4]).pairwise_product(vector(QQ[x],[1,2,3,4]))) 
Ambient free module of rank 4 over the integral domain Univariate Polynomial Ring in y over Univariate Polynomial Ring in x over Rational Field 
sage: parent(vector(QQ[y],[1,2,3,4]).pairwise_product(vector(ZZ[x][y],[1,2,3,4]))) 
Ambient free module of rank 4 over the integral domain Univariate Polynomial Ring in y over Univariate Polynomial Ring in x over Rational Field 
sage: parent(vector(ZZ[x][y],[1,2,3,4]).pairwise_product(vector(QQ[y],[1,2,3,4]))) 
Ambient free module of rank 4 over the integral domain Univariate Polynomial Ring in y over Univariate Polynomial Ring in x over Rational Field 
sage: parent(vector(ZZ[x],[1,2,3,4]).pairwise_product(vector(ZZ[y],[1,2,3,4]))) 
... 
TypeError: no common canonical parent for objects with parents: 'Ambient free module of rank 4 over the integral domain Univariate Polynomial Ring in x over Integer Ring' and 'Ambient free module of rank 4 over the integral domain Univariate Polynomial Ring in y over Integer Ring'
sage: parent(vector(ZZ[x],[1,2,3,4]).pairwise_product(vector(QQ[y],[1,2,3,4]))) 
... 
TypeError: no common canonical parent for objects with parents: 'Ambient free module of rank 4 over the integral domain Univariate Polynomial Ring in x over Integer Ring' and 'Ambient free module of rank 4 over the principal ideal domain Univariate Polynomial Ring in y over Rational Field'
sage: parent(vector(QQ[x],[1,2,3,4]).pairwise_product(vector(ZZ[y],[1,2,3,4]))) 
... 
TypeError: no common canonical parent for objects with parents: 'Ambient free module of rank 4 over the principal ideal domain Univariate Polynomial Ring in x over Rational Field' and 'Ambient free module of rank 4 over the integral domain Univariate Polynomial Ring in y over Integer Ring'
sage: parent(vector(QQ[x],[1,2,3,4]).pairwise_product(vector(QQ[y],[1,2,3,4]))) 
... 
TypeError: no common canonical parent for objects with parents: 'Ambient free module of rank 4 over the principal ideal domain Univariate Polynomial Ring in x over Rational Field' and 'Ambient free module of rank 4 over the principal ideal domain Univariate Polynomial Ring in y over Rational Field'
sage: v = vector({1: 1, 3: 2})  # test sparse vectors
sage: w = vector({0: 6, 3: -4})
sage: v.pairwise_product(w)
(0, 0, 0, -8)
sage: w.pairwise_product(v) == v.pairwise_product(w)
True
plot(plot_type, **kwds=None)

INPUT:

  • plot_type - (default: ‘arrow’ if v has 3 or fewer components,

    otherwise ‘step’) type of plot. Options are:

    • ‘arrow’ to draw an arrow
    • ‘point’ to draw a point at the coordinates specified by the vector
    • ‘step’ to draw a step function representing the coordinates of the vector.

    Both ‘arrow’ and ‘point’ raise exceptions if the vector has more than 3 dimensions.

EXAMPLES:

sage: v = vector(RDF, (1,2))
sage: eps = 0.1
sage: plot(v, plot_type='arrow')
sage: plot(v, plot_type='point')
sage: plot(v, plot_type='step') # calls v.plot_step()
sage: plot(v, plot_type='step', eps=eps, xmax=5, hue=0)
sage: v = vector(RDF, (1,2,1))
sage: plot(v) # defaults to an arrow plot
sage: plot(v, plot_type='arrow')
sage: from sage.plot.plot3d.shapes2 import frame3d
sage: plot(v, plot_type='point')+frame3d((0,0,0), v.list())
sage: plot(v, plot_type='step') # calls v.plot_step()
sage: plot(v, plot_type='step', eps=eps, xmax=5, hue=0)
sage: v = vector(RDF, (1,2,3,4))
sage: plot(v) # defaults to a step plot
plot_step(xmin, xmax=0, eps=1, res=None, connect=None, **kwds=True)

INPUT:

  • xmin - (default: 0) start x position to start plotting
  • xmax - (default: 1) stop x position to stop plotting
  • eps - (default: determined by xmax) we view this vector as defining a function at the points xmin, xmin + eps, xmin + 2*eps, ...,
  • res - (default: all points) total number of points to include in the graph
  • connect - (default: True) if True draws a line; otherwise draw a list of points.

EXAMPLES:

sage: eps=0.1
sage: v = vector(RDF, [sin(n*eps) for n in range(100)])
sage: v.plot_step(eps=eps, xmax=5, hue=0)
set(i, x)
set is meant to be more efficient than setitem, because it does not do any error checking or coercion. Use with care.
set_immutable()

Make this vector immutable. This operation can’t be undone.

EXAMPLES:

sage: v = vector([1..5]); v
(1, 2, 3, 4, 5)
sage: v[1] = 10
sage: v.set_immutable()
sage: v[1] = 10
Traceback (most recent call last):
...
ValueError: vector is immutable; please change a copy instead (use copy())
sparse_vector()
subs(in_dict, **kwds=None)

EXAMPLES:

sage: var('a,b,d,e')
(a, b, d, e)
sage: v = vector([a, b, d, e])
sage: v.substitute(a=1)
(1, b, d, e)
sage: v.subs(a=b, b=d)
(b, d, d, e)
support()
Return the integers i such that self[i] != 0. This is the same as the nonzero_positions function.
transpose()

EXAMPLES:

sage: v = vector(ZZ, [2, 12, 22])
sage: transpose(vector(v))
[ 2]
[12]
[22]
sage: transpose(vector(GF(7), v))
[2]
[5]
[1]
sage: transpose(vector(v, ZZ['x', 'y']))
[ 2]
[12]
[22]
class sage.modules.free_module_element.FreeModuleElement_generic_dense

Bases: sage.modules.free_module_element.FreeModuleElement

A generic dense element of a free module.

list(copy=True)
n(*args, **kwargs)

Returns a numerical approximation of self by calling the n() method on all of its entries.

EXAMPLES:

sage: v = vector(RealField(212), [1,2,3])
sage: v.n()
(1.00000000000000, 2.00000000000000, 3.00000000000000)
sage: _.parent()
Vector space of dimension 3 over Real Field with 53 bits of precision
sage: v.n(prec=75)
(1.000000000000000000000, 2.000000000000000000000, 3.000000000000000000000)
sage: _.parent()
Vector space of dimension 3 over Real Field with 75 bits of precision
class sage.modules.free_module_element.FreeModuleElement_generic_sparse

Bases: sage.modules.free_module_element.FreeModuleElement

A generic sparse free module element is a dictionary with keys ints i and entries in the base ring.

EXAMPLES:

Pickling works:

sage: v = FreeModule(ZZ, 3, sparse=True).0
sage: loads(dumps(v)) == v
True
sage: v = FreeModule(Integers(8)['x,y'], 5, sparse=True).1
sage: loads(dumps(v)) - v
(0, 0, 0, 0, 0)
sage: a = vector([-1,0,1/1],sparse=True); b = vector([-1/1,0,0],sparse=True)
sage: a.parent()
Sparse vector space of dimension 3 over Rational Field
sage: b - a
(0, 0, -1)
sage: (b-a).dict()
{2: -1}
denominator()
dict(copy=True)
get(i)
Like __getitem__ but with no type or bounds checking. Returns 0 if access is out of bounds.
iteritems()
list(copy=True)
n(*args, **kwargs)

Returns a numerical approximation of self by calling the n() method on all of its entries.

EXAMPLES:

sage: v = vector(RealField(200), [1,2,3], sparse=True)
sage: v.n()
(1.00000000000000, 2.00000000000000, 3.00000000000000)
sage: _.parent()
Sparse vector space of dimension 3 over Real Field with 53 bits of precision
sage: v.n(prec=75)
(1.000000000000000000000, 2.000000000000000000000, 3.000000000000000000000)
sage: _.parent()
Sparse vector space of dimension 3 over Real Field with 75 bits of precision
nonzero_positions()

Returns the list of numbers i such that self[i] != 0.

EXAMPLES:

sage: v = vector({1: 1, 3: -2})
sage: w = vector({1: 4, 3: 2})
sage: v+w
(0, 5, 0, 0)
sage: (v+w).nonzero_positions()
[1]
set(i, x)
Like __setitem__ but with no type or bounds checking.
sage.modules.free_module_element.free_module_element(arg0, arg1=None, arg2=None, sparse=None)

Return a vector over R with given entries.

CALL FORMATS:

  1. vector(object)
  2. vector(ring, object)
  3. vector(object, ring)
  4. vector(numpy_array)

In each case, give sparse=True or sparse=False as an option.

INPUT:

  • elts - entries of a vector (either a list or dict).
  • R - ring
  • sparse - optional

OUTPUT: An element of the free module over R of rank len(elts).

EXAMPLES:

sage: v = vector([1,2,3]); v
(1, 2, 3)
sage: v.parent()
Ambient free module of rank 3 over the principal ideal domain Integer Ring
sage: v = vector([1,2,3/5]); v
(1, 2, 3/5)
sage: v.parent()
Vector space of dimension 3 over Rational Field

All entries must canonically coerce to some common ring:

sage: v = vector([17, GF(11)(5), 19/3]); v
Traceback (most recent call last):
...
TypeError: unable to find a common ring for all elements
sage: v = vector([17, GF(11)(5), 19]); v
(6, 5, 8)
sage: v.parent()
Vector space of dimension 3 over Finite Field of size 11
sage: v = vector([17, GF(11)(5), 19], QQ); v
(17, 5, 19)
sage: v.parent()
Vector space of dimension 3 over Rational Field
sage: v = vector((1,2,3), QQ); v
(1, 2, 3)
sage: v.parent()
Vector space of dimension 3 over Rational Field
sage: v = vector(QQ, (1,2,3)); v
(1, 2, 3)
sage: v.parent()
Vector space of dimension 3 over Rational Field
sage: v = vector(vector([1,2,3])); v
(1, 2, 3)
sage: v.parent()
Ambient free module of rank 3 over the principal ideal domain Integer Ring

You can also use free_module_element, which is the same as vector.

sage: free_module_element([1/3, -4/5])
(1/3, -4/5)

Make a vector mod 3 out of a vector over \ZZ:

sage: vector(vector([1,2,3]), GF(3))
(1, 2, 0)

Here we illustrate the creation of sparse vectors by using a dictionary:

sage: vector({1:1.1, 3:3.14})
(0.000000000000000, 1.10000000000000, 0.000000000000000, 3.14000000000000)

Any 1 dimensional numpy array of type float or complex may be passed to vector. The result will be a vector in the appropriate dimensional vector space over the real double field or the complex double field. The data in the array must be contiguous so column-wise slices of numpy matrices will raise an exception.

sage: import numpy
sage: x=numpy.random.randn(10)
sage: y=vector(x)
sage: v=numpy.random.randn(10)*numpy.complex(0,1)
sage: w=vector(v)

If any of the arguments to vector have Python type int, long, real, or complex, they will first be coerced to the appropriate Sage objects. This fixes trac #3847:

sage: v = vector([int(0)]); v
(0)
sage: v[0].parent()
Integer Ring
sage: v = vector(range(10)); v
(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
sage: v[3].parent()
Integer Ring
sage: v = vector([float(23.4), int(2), complex(2+7*I), long(1)]); v
(23.4, 2.0, 2.0 + 7.0*I, 1.0)
sage: v[1].parent()
Complex Double Field

If the argument is a vector, it doesn’t change the base ring. This fixes trac #6643:

sage: K.<sqrt3> = QuadraticField(3)
sage: u = vector(K, (1/2, sqrt3/2) )
sage: vector(u).base_ring()
Number Field in sqrt3 with defining polynomial x^2 - 3
sage: v = vector(K, (0, 1) )
sage: vector(v).base_ring()
Number Field in sqrt3 with defining polynomial x^2 - 3
sage.modules.free_module_element.is_FreeModuleElement(x)
sage.modules.free_module_element.make_FreeModuleElement_generic_dense(parent, entries, degree)
sage.modules.free_module_element.make_FreeModuleElement_generic_dense_v1(parent, entries, degree, is_mutable)
sage.modules.free_module_element.make_FreeModuleElement_generic_sparse(parent, entries, degree)
sage.modules.free_module_element.make_FreeModuleElement_generic_sparse_v1(parent, entries, degree, is_mutable)
sage.modules.free_module_element.prepare(v, R)
sage.modules.free_module_element.prepare_dict(w, R)

EXAMPLES:

sage: from sage.modules.free_module_element import prepare_dict
sage: prepare_dict({3:1 , 5:3}, QQ)
([0, 0, 0, 1, 0, 3], Rational Field)
sage: prepare_dict({},QQ)
([], Rational Field)
sage.modules.free_module_element.vector(arg0, arg1=None, arg2=None, sparse=None)

Return a vector over R with given entries.

CALL FORMATS:

  1. vector(object)
  2. vector(ring, object)
  3. vector(object, ring)
  4. vector(numpy_array)

In each case, give sparse=True or sparse=False as an option.

INPUT:

  • elts - entries of a vector (either a list or dict).
  • R - ring
  • sparse - optional

OUTPUT: An element of the free module over R of rank len(elts).

EXAMPLES:

sage: v = vector([1,2,3]); v
(1, 2, 3)
sage: v.parent()
Ambient free module of rank 3 over the principal ideal domain Integer Ring
sage: v = vector([1,2,3/5]); v
(1, 2, 3/5)
sage: v.parent()
Vector space of dimension 3 over Rational Field

All entries must canonically coerce to some common ring:

sage: v = vector([17, GF(11)(5), 19/3]); v
Traceback (most recent call last):
...
TypeError: unable to find a common ring for all elements
sage: v = vector([17, GF(11)(5), 19]); v
(6, 5, 8)
sage: v.parent()
Vector space of dimension 3 over Finite Field of size 11
sage: v = vector([17, GF(11)(5), 19], QQ); v
(17, 5, 19)
sage: v.parent()
Vector space of dimension 3 over Rational Field
sage: v = vector((1,2,3), QQ); v
(1, 2, 3)
sage: v.parent()
Vector space of dimension 3 over Rational Field
sage: v = vector(QQ, (1,2,3)); v
(1, 2, 3)
sage: v.parent()
Vector space of dimension 3 over Rational Field
sage: v = vector(vector([1,2,3])); v
(1, 2, 3)
sage: v.parent()
Ambient free module of rank 3 over the principal ideal domain Integer Ring

You can also use free_module_element, which is the same as vector.

sage: free_module_element([1/3, -4/5])
(1/3, -4/5)

Make a vector mod 3 out of a vector over \ZZ:

sage: vector(vector([1,2,3]), GF(3))
(1, 2, 0)

Here we illustrate the creation of sparse vectors by using a dictionary:

sage: vector({1:1.1, 3:3.14})
(0.000000000000000, 1.10000000000000, 0.000000000000000, 3.14000000000000)

Any 1 dimensional numpy array of type float or complex may be passed to vector. The result will be a vector in the appropriate dimensional vector space over the real double field or the complex double field. The data in the array must be contiguous so column-wise slices of numpy matrices will raise an exception.

sage: import numpy
sage: x=numpy.random.randn(10)
sage: y=vector(x)
sage: v=numpy.random.randn(10)*numpy.complex(0,1)
sage: w=vector(v)

If any of the arguments to vector have Python type int, long, real, or complex, they will first be coerced to the appropriate Sage objects. This fixes trac #3847:

sage: v = vector([int(0)]); v
(0)
sage: v[0].parent()
Integer Ring
sage: v = vector(range(10)); v
(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
sage: v[3].parent()
Integer Ring
sage: v = vector([float(23.4), int(2), complex(2+7*I), long(1)]); v
(23.4, 2.0, 2.0 + 7.0*I, 1.0)
sage: v[1].parent()
Complex Double Field

If the argument is a vector, it doesn’t change the base ring. This fixes trac #6643:

sage: K.<sqrt3> = QuadraticField(3)
sage: u = vector(K, (1/2, sqrt3/2) )
sage: vector(u).base_ring()
Number Field in sqrt3 with defining polynomial x^2 - 3
sage: v = vector(K, (0, 1) )
sage: vector(v).base_ring()
Number Field in sqrt3 with defining polynomial x^2 - 3

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