Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2012

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: How to easily set up all coefficients to be positive in Solving an integer equation?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg124335] Re: How to easily set up all coefficients to be positive in Solving an integer equation?
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Tue, 17 Jan 2012 03:25:12 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Either of these should work (if n is known, e.g. 10):

Thread[Array[x, 10] > 0]

{x[1] > 0, x[2] > 0, x[3] > 0, x[4] > 0, x[5] > 0, x[6] > 0, x[7] > 0,
   x[8] > 0, x[9] > 0, x[10] > 0}

And @@ Thread[Array[x, 10] > 0]

x[1] > 0 && x[2] > 0 && x[3] > 0 && x[4] > 0 && x[5] > 0 && x[6] > 0 &&
   x[7] > 0 && x[8] > 0 && x[9] > 0 && x[10] > 0

If n is NOT known, nothing will work.

Bobby

On Mon, 16 Jan 2012 16:11:13 -0600, Rex <aoirex at gmail.com> wrote:

> Given a vector `A==[a_1, a_2, a_3,...,a_n]`, where a_i are integers,
> now
> solving an equation
> `=E2=88=91a_i * x_i==0` with all x_i>==0, and x_i to be integers.
>
> We can write some code like this
> `Solve[A . Table[x[i], {i, n}] ==  0 && Table[x[i] > 0, {i, n}],
> Integers]`
>
> But the conditions above `Table[x[i] > 0` is not rightly coded. That
> should be
> `x[1]>0 && x[2]>0 && x[3]>0 &&...x[n]>0`
> Is there any easy way to write such code?
>


-- 
DrMajorBob at yahoo.com



  • Prev by Date: Re: NDSolve output without interpolating function
  • Next by Date: Re: Question about DeleteCases to remove list elements based on first character
  • Previous by thread: Re: How to easily set up all coefficients to be positive in Solving an integer equation?
  • Next by thread: Hatching triangle interior