Radovan Omorjan | 1 Jan 09:01 2008
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Re: Solving linear algebraic eqns. in vector (matrix) notation ?

I've figured out myself how to solve this. It took me some time to 
realise that equations and unknowns have to be in lists in order to 
solve them with "solve" or "linsolve". I also realised that I do not 
need "eigen". Something like transforming matrix m into equation list like:

(%i9) eqns : makelist(m[i][1]=0,i,1,6);
(%o9) [- n2  + n1  - eps  = 0, - n2  + n1  - eps  + eps  = 0,
            1     1      1          2     2      2      1
                                                              eps    eps
                                                                 2      1
- n2  + n1  + eps  = 0, - n2  + n1  + eps  = 0, - n2  + n1  - ---- - 
---- = 0,
    3     3      2          4     4      1          5     5    2      2
n1  - n2  = 0]
  6     6

and solving by:

(%i10) linsolve(eqns,n2);
(%o10) [n2  = n1  - eps , n2  = n1  - eps  + eps , n2  = n1  + eps ,
          1     1      1    2     2      2      1    3     3      2
                                              - 2 n1  + eps  + eps
                                                    5      2      1
                    n2  = n1  + eps , n2  = - ---------------------, n2  
= n1 ]
                      4     4      1    5               2              
6     6

will do the job. I should have read the manual more carefuly, sorry. 
Anyway, I've learned some new things.
(Continue reading)

Viktor T. Toth | 2 Jan 00:26 2008

Re: itensor - contracting antisymmetric and symmetric indices

In theory, Itensor should be able to do this:

(%i1) load(itensor)$
(%i2) decsym(A,2,0,[anti(all)],[]);
(%o2)                                done
(%i3) decsym(S,0,2,[],[sym(all)]);
(%o3)                                done
(%i4) ishow(A([i,j],[])*S([],[i,j]))$
                                    i j
(%t4)                              S    A
                                         i j
(%i5) canform(%);
(%o5)                                  0

Well, it doesn't, not yet anyway. It's on my rather longish to-do list. In
the meantime, here's an alternative that may be sometimes useful:

(%i1) load(itensor)$
(%i2) decsym(S,0,2,[],[sym(all)]);
(%o2)                                done
(%i3) components(A([i,j],[]),1/2*(aa([i,j],[])-aa([j,i],[])));
(%o3)                                done
(%i4) ishow('A([i,j],[])*S([],[i,j]))$
                                    i j
(%t4)                              S    A
                                         i j
(%i5) canform(ev(%,A));
(%o5)                                  0

Viktor
(Continue reading)

Mansur Marvanov | 1 Jan 16:19 2008
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matrices to plot'ing list

Hello!

I have 2 matrix 11x1:

(%i1) x:matrix([-3.6],[-3.08],[-2.56],[-2.04],[-1.52],[-1],[-0.48],[0.04],[0.56],[1.08],[1.6])$

(%i2) y:matrix([-2.397],[-0.401],[-0.577],[-1.268],[-0.933],[-0.359],[1.107],[1.300],[1.703],[-0.299],[-1.417])$

What's the easy way to plot this 11 points? My problem is to transform
this 2 matrices to this style:

(%i12) xx:[10, 20, 30, 40, 50]$
(%i13) yy:[.6, .9, 1.1, 1.3, 1.4]$
(%i14) xy:[[10,.6], [20,.9], [30,1.1], [40,1.3], [50,1.4]]$
Wolfgang Lindner | 2 Jan 09:01 2008
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Re: matrices to plot'ing list

dear Mansur,

please look at the functions of package 'draw', e.g. points.
There you will find many examples.
Package 'descriptive' should offer possibilities, too.

HTH Wolfgang

"Mansur Marvanov" <nanorobocop <at> gmail.com> schrieb:
> Hello!
> 
> I have 2 matrix 11x1:
> 
> (%i1) x:matrix([-3.6],[-3.08],[-2.56],[-2.04],[-1.52],[-1],[-0.48],[0.04],[0.56],[1.08],[1.6])$
> 
> (%i2) y:matrix([-2.397],[-0.401],[-0.577],[-1.268],[-0.933],[-0.359],[1.107],[1.300],[1.703],[-0.299],[-1.417])$
> 
> What's the easy way to plot this 11 points? My problem is to transform
> this 2 matrices to this style:
> 
> (%i12) xx:[10, 20, 30, 40, 50]$
> (%i13) yy:[.6, .9, 1.1, 1.3, 1.4]$
> (%i14) xy:[[10,.6], [20,.9], [30,1.1], [40,1.3], [50,1.4]]$
> _______________________________________________
> Maxima mailing list
> Maxima <at> math.utexas.edu
> http://www.math.utexas.edu/mailman/listinfo/maxima
Barton Willis | 2 Jan 12:19 2008

Re: Rounding

Try ceiling, floor, and round.

Barton

-----maxima-bounces <at> math.utexas.edu wrote: -----

>To: maxima <at> math.utexas.edu
>From: Holger Schulz <qdl <at> gmx.net>
>Sent by: maxima-bounces <at> math.utexas.edu
>Date: 01/02/2008 05:45AM
>Subject: [Maxima] Rounding
>
>I haven't found functions for rounding/truncating rational numbers
>yet. Are there some? How are they called?
>
>Thanks
>
>hs
>_______________________________________________
>Maxima mailing list
>Maxima <at> math.utexas.edu
>http://www.math.utexas.edu/mailman/listinfo/maxima
van Nek | 2 Jan 12:28 2008
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Re: Rounding

Holger,

there are 'floor' and 'ceiling', which do what their names suggest. 

(%i1) floor(-22/3);
(%o1)                                 - 8
(%i2) ceiling(-22/3);
(%o2)                                 - 7

They can deal with more than only rational numbers. Type
? floor
or
? ceiling 
for more information.

Also there are 'fix' and 'entier' (two names for one function), which as far as I know do 
nothing different than 'floor'.

Volker van Nek

Am 2 Jan 2008 um 11:45 hat Holger Schulz geschrieben:

> I haven't found functions for rounding/truncating rational numbers 
> yet. Are there some? How are they called?
> 
> Thanks
> 
> hs
> _______________________________________________
> Maxima mailing list
(Continue reading)

Mario Rodriguez | 2 Jan 13:04 2008
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Re: matrices to plot'ing list


> (%i1) x:matrix([-3.6],[-3.08],[-2.56],[-2.04],[-1.52],[-1],[-0.48],[0.04],[0.56],[1.08],[1.6])$
>
> (%i2) y:matrix([-2.397],[-0.401],[-0.577],[-1.268],[-0.933],[-0.359],[1.107],[1.300],[1.703],[-0.299],[-1.417])$
>
> What's the easy way to plot this 11 points? 
>   

load(draw)$
draw2d(points(addcol(x,y)))$

--

-- 
Mario Rodriguez Riotorto
www.biomates.net
Jaime Villate | 2 Jan 13:27 2008
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Re: matrices to plot'ing list


On Tue, 2008-01-01 at 18:19 +0300, Mansur Marvanov wrote:
> I have 2 matrix 11x1:
> 
> (%i1) x:matrix([-3.6],[-3.08],[-2.56],[-2.04],[-1.52],[-1],[-0.48],[0.04],[0.56],[1.08],[1.6])$
> 
> (%i2) y:matrix([-2.397],[-0.401],[-0.577],[-1.268],[-0.933],[-0.359],[1.107],[1.300],[1.703],[-0.299],[-1.417])$
> 
> What's the easy way to plot this 11 points? My problem is to transform
> this 2 matrices to this style:
> 
> (%i12) xx:[10, 20, 30, 40, 50]$
> (%i13) yy:[.6, .9, 1.1, 1.3, 1.4]$
> (%i14) xy:[[10,.6], [20,.9], [30,1.1], [40,1.3], [50,1.4]]$

Wolfgang Lindner has already told you what he thinks is the easiest way.
In my opinion, the easiest way is the following:

(%i3) xx: transpose(x)[1]$

(%i4) yy: transpose(y)[1]$

(%i5) plot2d([discrete,xx,yy],[style,points])$

Regards,
Jaime Villate
Jaime Villate | 2 Jan 16:39 2008
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Re: Evaluating boolean expressions


On Wed, 2008-01-02 at 13:50 +0100, Holger Schulz wrote:
> but that doesn't work for boolean expression. I expected 5>3 to be  
> evaluated to true. But it wasn't:
> 
> 
> (%i42) 5>3;
> 
> (%o42) 5>3
> 
> Is there any trick to force the evaluation of boolean expressions?

(%i1) is(5>3);
(%o1) true
Mario Rodriguez | 2 Jan 16:41 2008
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Re: Evaluating boolean expressions

Holger Schulz escribió:
> Numeric expressions are evaluated, like
>
> (%i37) 5-3;
>
> (%o37) 2
>
> but that doesn't work for boolean expression. I expected 5>3 to be  
> evaluated to true. But it wasn't:
>
>
> (%i42) 5>3;
>
> (%o42) 5>3
>
> Is there any trick to force the evaluation of boolean expressions?
>
>   
try

is(5>3);

The 'is' command is not necessary in other contexts:

if 5>3 then 1 else 0;

or

5>3 or 2>4;

(Continue reading)


Gmane