Re: [sage-support] Approximate decimal answers

[William Stein]

On Tuesday, March 24, 2015,  wrote:

>  When using Sage. my students really like using the n() method as in
> show(sqrt(2).n(digits=50))
> giving the result rounded off to 50 decimal digits after the decimal point.
>
> What I'm wondering is where does the n() method come from. Is it peculiar
> to Sage or Maxima or what? Is it pure python? The reason I ask is that some
> of my independent study student are using mpi4py in openMPI on a Linux
> Cluster they put together doing some simple Monte Carlo simulations and
> quadrature calculations. If n() is pure python, I'd like to give them the
> code so they can get more digits out of their simulations
>

Cython. Built into Sage.  It's a method on symbolic expressions that
evaluates the leaves to the given precision then simplifies the result by
evaluating the whole tree to get a single number.



>
>
> Is this doable? What do you think?
>
> TIA,
> A. Jorge Garcia
> http://shadowfaxrant.blogspot.com
>








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[sage-support] Approximate decimal answers

[calcpage]

When using Sage. my students really like using the n() method as in
show(sqrt(2).n(digits=50)) 
giving the result rounded off to 50 decimal digits after the decimal point.

What I'm wondering is where does the n() method come from. Is it peculiar to 
Sage or Maxima or what? Is it pure python? The reason I ask is that some of my 
independent study student are using mpi4py in openMPI on a Linux Cluster they 
put together doing some simple Monte Carlo simulations and quadrature 
calculations. If n() is pure python, I'd like to give them the code so they can 
get more digits out of their simulations.

Is this doable? What do you think?

TIA,
A. Jorge Garcia
http://shadowfaxrant.blogspot.com 

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[sage-support] is it possible to install only the core software, and download packages when i need them?

[Alexey Muranov]

Hello,

i find Sage distributions downloadable from its web site huge, and most 
likely i will never need most of the functions.  Is it possible to install 
only the core, and download needed packages on demand?

Thank you,

Alexey.

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[sage-support] Re: Filling a matrix with functions

[Oscar Alberto Castillo Felisola]

Thank you very much Harald!

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[sage-support] Re: Filling a matrix with functions

[Harald Schilly]

On Tuesday, March 24, 2015 at 12:49:57 PM UTC+1, Oscar Alberto Castillo 
Felisola wrote:
>
> I'd like to obtain something like
>
> f11 = function('f11', t,r)
> f12 = function('f12', t,r)
> f21 = function('f21', t,r)
> f22 = function('f22', t,r)
> M = matrix(2,2, [[f11, f12], [f21, f22]])
>
>
 
Since this is doable via a functional mapping from the indices to the 
desired objects, you can use the matrix to do this via the lambda operator:

sage: var("t r")
(t, r)
sage: matrix(5, 5, lambda x,y : function("f%s%s" % (x,y), t, r))
[f00(t, r) f01(t, r) f02(t, r) f03(t, r) f04(t, r)]
[f10(t, r) f11(t, r) f12(t, r) f13(t, r) f14(t, r)]
[f20(t, r) f21(t, r) f22(t, r) f23(t, r) f24(t, r)]
[f30(t, r) f31(t, r) f32(t, r) f33(t, r) f34(t, r)]
[f40(t, r) f41(t, r) f42(t, r) f43(t, r) f44(t, r)]

It's zero-based indexed, as everything else in Python, but you can fix it 
easily. Hope this helps.

-- Harald



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[sage-support] Re: Filling a matrix with functions

[Oscar Alberto Castillo Felisola]

I'd like to obtain something like

f11 = function('f11', t,r)
f12 = function('f12', t,r)
f21 = function('f21', t,r)
f22 = function('f22', t,r)
M = matrix(2,2, [[f11, f12], [f21, f22]])

Note that in principle all the functions depend on the same variables.

If the assignation of functions could be used as components of a metric of 
sagemanifold, would be even better.

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[sage-support] Re: Filling a matrix with functions

[Harald Schilly]

On Tuesday, March 24, 2015 at 11:05:21 AM UTC+1, Oscar Alberto Castillo 
Felisola wrote:
>
> but for "huge" matrices it is boring and make no sense. 
>

Can you describe a rule or pattern how this matrix should be filled? 

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[sage-support] Filling a matrix with functions

[Oscar Alberto Castillo Felisola]

Hi. I know that one can define a function by declaring

sage: f = function('f', t,r)

However, I'm interested in declaring a matrix filled with different 
functions. Of course, for a small matrix I can do it by hand, but for 
"huge" matrices it is boring and make no sense. 

Is it possible to do what I need? 

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Re: [sage-support] solving equation involving absolute values

[sundar]

   Some documentation of maxima's to_poly_solve command is on 

> http://maxima.sourceforge.net/docs/manual/de/maxima_75.html, 
> about 3/4th down the page. 
>
>
>
Thanks. But is there other way to solve this particular equation ?

 

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Re: [sage-support] solving equation involving absolute values

[David Joyner]

On Tue, Mar 24, 2015 at 1:04 AM, sundar  wrote:
> Hello
>
> I am newbie to sagemath. I have windows 8 and sage version is 6.4.1. I am
> running it inside virtualbox.
> I was reading some thing about solving equations on sage website at
> http://www.sagemath.org/doc/reference/calculus/sage/symbolic/relation.html
>
> At one point author is trying to demonstrate the use of optional keywords
> for the "solve"
> He is solving equation
>
> solve(abs(1-abs(1-x)) == 10, x)
>
> When evaluated this gives
>
> [abs(abs(x - 1) - 1) == 10]
>
> But when the input is modified a little as
>
> solve(abs(1-abs(1-x)) == 10, x, to_poly_solve=True)
>
> sage gives correct result as
> [x == -10, x == 12]
>
>
> So why does it not work in the first case ? I didn't understand this use of
> keyword to_poly_solve.
>

Some documentation of maxima's to_poly_solve command is on
http://maxima.sourceforge.net/docs/manual/de/maxima_75.html,
about 3/4th down the page.

> Please help
> sundar
>
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