# How to create a symbolic arbitrary dimensional zero vector?

one way:

sage: symbolic_expression(list(zero_vector(k)))
# k, dim. of vector, k is some fixed integer, e.g. k = 10,
# many thanks to @tmonteil 

but it is too long!!

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Can you make your wish more explicit ? Is k a fixed number ? Wich order of magnitude ?

( 2013-11-06 06:11:46 +0200 )edit

Sorry, it is some fixed integer, e.g. k = 10

( 2013-11-06 08:28:14 +0200 )edit

what do you mean by "it is too long" ?

( 2013-11-06 09:06:53 +0200 )edit

the length of the string "symbolic_expression(list(zero_vector(k)))", can we use some command like "zero_list(k)"?

( 2013-11-06 09:30:27 +0200 )edit

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You can make your expression shorter by typing:

sage: w = zero_vector(SR, 10) ; w
(0, 0, 0, 0, 0, 0, 0, 0, 0, 0)


You can check that it is the same object:

sage: v = symbolic_expression(list(zero_vector(10)))
sage: v
(0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
sage: v == w
True

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Thanks! Yes, that is what I want! SR = Symbolic Ring, super.

( 2013-11-06 09:32:38 +0200 )edit

Can we create a list whose entries are all 1, using a similar method?

( 2013-11-13 10:10:51 +0200 )edit

A version with 14 characters

sage: (SR^10).zero()
(0, 0, 0, 0, 0, 0, 0, 0, 0, 0)


that could even be shorten to 9

sage: (SR^10)()
(0, 0, 0, 0, 0, 0, 0, 0, 0, 0)

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For the follow-up question posted as a comment to @tmonteil's answer:

vector(SR, [1]*10)


is worth mentioning as well. Here, [1]*10 is just the Python way of constructing a list with 10 repeats of 1.

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This is an answer to the follow-up question posted as a comment to @tmonteil's answer.

There is no function ones_vector but we can define a vector of ones as the first row of a matrix of ones:

sage: v = matrix.ones(SR, 1, 10)[0]
sage: v
(1, 1, 1, 1, 1, 1, 1, 1, 1, 1)
sage: v.parent()
Vector space of dimension 10 over Symbolic Ring


It lives in the same space as the zero vector:

sage: u = zero_vector(SR, 10)
sage: u
(0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
sage: u.parent()
Vector space of dimension 10 over Symbolic Ring

more