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Re: few things would be nice to have in next version of

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114699] Re: few things would be nice to have in next version of
  • From: Oliver Ruebenkoenig <ruebenko at wolfram.com>
  • Date: Mon, 13 Dec 2010 03:53:36 -0500 (EST)
  • References: <201012100731.CAA06879@smc.vnet.net>

On Fri, 10 Dec 2010, Nasser M. Abbasi wrote:

> I thought I take a minute to write down few things before I
> forget them, that I think would be nice to have in Mathematica
>
> 1) Need an Incomplete Cholesky decomposition function. Could
> add an option to current Cholesky decomposition function to
> allow one to supply a drop tolerance value. Mathematica only
> has Cholesky decomposition


That seems doable. I have talked to the developer doing this and most 
likely put it on the agenda.

Btw. you can specify drop tolerances for the iterative linear solver. My 
experience with them however, is that fiddling out the values is more 
trouble than the performance gain achievable.

>
> 2) Function for Matrix condition number for dense matrices, and
> Matrix condition number estimator for sparse matrices. Both are
> missing now.

dense = RandomReal[{0, 1}, {5, 5}];
LinearAlgebra`MatrixConditionNumber[dense]

sparse = SparseArray[{Band[{1, 1}] -> -2, Band[{1, 2}] -> 1}, {5, 5}];
LinearAlgebra`MatrixConditionNumber[sparse]

As I said, I filed a suggestion that this is to be moved in System` 
context (with proper documentation)

Oliver

>
> 3) On the documentation center, if someone makes a typo, it would
> be nice if the system asked one "did you mean that?" and gave
> some options. (as Google does when one makes a typo in search)
>
> For example, typing ref/SHow gives an error because one did not
> type ref/show.
>
> 4) It would be nice to combine plots using Show[] and have an
> option for automatic styling so that the plots all come out
> with different colors.
>
> Doing
>
> p1=Plot[Sin[x],{x,-Pi,Pi}];
> p2=Plot[Cos[2 x],{x,-Pi,Pi}];
> Show[p1,p2]
>
> shows all plots with same color. One will have to give
> a PlotStyle to each separate plot before and have to
> think of different color to use which is not used by
> other plots.
>
> For convenience, it will be nice to have the system automatically
> pick different colors, and also have the legend be such that
> it matches the order the plots are put together. Similar to
> what one does with PlotLegend:
>
> Needs["PlotLegends`"]
> Plot[{Sin[x],Cos[x]},{x,-Pi,Pi},PlotLegend->{"sine","cosine"}]
>
> But have the above work with Show as well, as in:
>
> Show[p1,p2,ShowLegend->{"sine","cosine"}]
> and have each plot p_i (or graphic object p_i in general) be
> colored differently automatically and have this reflected in
> the legend generated (as what happens in PlotLegend).
>
> Speaking of PlotLegend, it would be nice to be able to adjust
> the location of it on the plot by using the mouse once the plot
> is rendered and be able to move it to different location by the
> mouse and adjust its size. I tried using V 8 with the new
> nice and improved drawing tools, but did not know how to do
> that yet. May be there is a way.
>
> I have few more, but need to work on that little more, may later
> will add to this post.
>
> thanks
> --Nasser
>
>


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