Re: [sage-support] The behavior of empty sums

2019-06-25 Thread 'luisfe' via sage-support
On Tuesday, June 25, 2019 at 10:03:03 AM UTC+2, Peter Luschny wrote: > > How that? Look at the output above. Sage *knows* that the terms of the sum > are polynomials. So it should return the zero of that ring, which is the > null polynomial. > > Not in the first case, look at what are you passi

Re: [sage-support] The behavior of empty sums

2019-06-17 Thread 'luisfe' via sage-support
On Monday, June 17, 2019 at 2:12:58 PM UTC+2, Peter Luschny wrote: As I see it the problem is that the sum runs over (0..n-1). > Thus for n = 0 it returns by convention the integer 0 for the > empty sum (is this correct?) which of course has no list. > > But shouldn't it return the null polynomi

Re: [sage-support] The behavior of empty sums

2019-06-17 Thread 'luisfe' via sage-support
On Monday, June 17, 2019 at 2:12:58 PM UTC+2, Peter Luschny wrote: As I see it the problem is that the sum runs over (0..n-1). > Thus for n = 0 it returns by convention the integer 0 for the > empty sum (is this correct?) which of course has no list. > > But shouldn't it return the null polynomia

Re: [sage-support] surface normal vector of polyhedron face

2019-02-27 Thread 'luisfe' via sage-support
On Wednesday, February 27, 2019 at 2:52:36 PM UTC+1, Daniel Krenn wrote: > > I suppose in non-full-dimensional case you still can use > > P.inequalities() as above, > > projecting them on the affine hull of P. > > Yes, this is the interesting case. The problem then is going back from > the p

[sage-support] Re: differences between the "image()" and "column_space()" commands on a matrix

2017-05-09 Thread 'luisfe' via sage-support
Sage interprets that matrices M acts on row vectors v on the left, v*M so in fact the method image corresponds to row_space >From the help of image: Return the image of the homomorphism on *rows* defined by this matrix. -- You received this message because you are subscribed to the Google Gro

[sage-support] Re: Expression to polynomial

2015-06-12 Thread 'luisfe' via sage-support
On Friday, June 12, 2015 at 11:17:37 AM UTC+2, NĂ©stor wrote: > Hello, > > I've got a rational expression in sage and I would like to convert it to a > polynomial with coefficients in some fraction field. > > More precisely, I've got something like this: > > a , x = var( 'a , x' ) ; > P = x/a ; >

[sage-support] Re: About finding roots of polynomials in specific domains

2015-06-12 Thread 'luisfe' via sage-support
On Thursday, June 11, 2015 at 5:26:28 PM UTC+2, Phoenix wrote: > I have two polynomials $p(x)$ and $q(x)$ and I want to know if there are > roots of the equation $\frac{p'}{p} = \frac{q'}{q}$ in the domain > $(a,\infinity)$ - where $a = max \{ roots(p),roots(q) \}$ > > This is the same as asking

[sage-support] Re: elements of a field extensions

2015-06-10 Thread 'luisfe' via sage-support
On Tuesday, June 9, 2015 at 5:36:01 PM UTC+2, black...@gmx.de wrote: > > Thank you, > > and i already tried this. In this case it obiously does work but in case i > have denominators, can u explain me how to solve it? > for example: K(s/(s+t),s^2*t^2) then i have to calculate the elimination >

[sage-support] Re: elements of a field extensions

2015-06-09 Thread 'luisfe' via sage-support
Have you tried using elimination ideals? K=QQ['s,t,a0,a1,a2'] K.inject_variables() I = Ideal( a0-s^2, a1-t^2, a2 - (s^2+t^2)) I.elimination_ideal([s,t]) Ideal (a0 + a1 - a2) of Multivariate Polynomial Ring in s, t, a0, a1, a2 over Rational Field So a2 = a0 + a1 The elimination ideal tells you wh

[sage-support] Re: Homomorphism from power series ring to residue field

2015-06-09 Thread 'luisfe' via sage-support
Within a specific interactive session, you could do the following, when creating the rings: sage: R = PowerSeriesRing(GF(2),'t') sage: F = R.residue_field() sage: phi = R.hom([0], F) sage: F.register_coercion(phi) This way, you are indicating that the morphism phi should be considered a coercio

[sage-support] Re: Typo in provided documentation

2014-10-02 Thread 'luisfe' via sage-support
It looks right to me. I am not a native English speaker so I could be (very) wrong, but I understand that the comparison x<2 is evaluated, which is completely true, independently if the condition is evaluated as True or False. In fact, next lines tell why x<2 is evaluated False and that h(x) re

[sage-support] Re: Computing Grobner Basis for general coefficients denoted by some variables.

2014-09-20 Thread &#x27;luisfe&#x27; via sage-support
In general, I prefer to put the parameters a_i as variables and then interpret the results. Another approach you may try is to work in the field: GF(2^d)['a_1,a_2,a_3'].fraction_field()['x_1,x_2,x_3'] but then you may encounter specialiation problems with denominators, another problem is that