Consider this piece of code:
sage: n=4 # dimension of state-space sage: x = polygens(QQ, ['x'+str(i) for i in [1..n]]); x # vector of state variables (x1, x2, x3, x4)
There is a handy keyword with formal power series, the number of generators (
num_gens), and it works like:
sage: PowerSeriesRing(QQ, 'x', num_gens=5) Multivariate Power Series Ring in x0, x1, x2, x3, x4 over Rational Field
There is a kind of analogue with polynomials, but not keyworded:
sage: PolynomialRing(QQ, 'x', 5) Multivariate Polynomial Ring in x0, x1, x2, x3, x4 over Rational Field
Is it possible to use any of these to define a vector of polynomial variables in the object
x as the beginning (but without list comprehension)?
As a side note, i think the
var constructor also lacks a vector form?
sage: var(['x'+str(i) for i in [1..n]]) (x1, x2, x3, x4)
This could be useful to simplify constructions as:
sage: A = matrix(SR, [['a'+str(i)+str(j) for j in [1..n]] for i in [1..n]]); A [a11 a12 a13 a14] [a21 a22 a23 a24] [a31 a32 a33 a34] [a41 a42 a43 a44]
In Matlab this is
A = sym('a', n), but i didn't find a similar shortcut in Sage.