treelayout and spaugment procedures

[David Bateman]

Ivana Varekova wrote:
> Hello,
> I want to ask whether there is anybody working on spaugment and 
> treelayout procedure?  I want to choose/implement some projects which 
> are on todo list now - but I'm not sure whether the list is up-to-date.
> Is there any other sparse matrix related project which will be fine to 
> be done?
> Thanks.
> Ivana Varekova
>
spaugment is trivial and already in 3.1.51+. The code is basically

[m, n] = size (a);
s = [ c * speye(m, m), a; a', sparse(n, n)];

as for treelayout, it was you who wrote treeplot, and treelayout is 90% 
of the treeplot function, so splitting up treeplot appropriately will 
give most of the treelayout function. At the time you wrote treeplot our 
exchange was

<quote>
>  Just one question, it seems to me that the treelayout function of matlab
>  is basically treeplot with a few extra details. I'm not really that
>  familar with graph theory and don't see that treelayout is necessarily
>  useful on its own, but perhaps it would be better to write treelayout
>  and use it to simplify treeplot.

You are right treeplot function is almost the same as treeplot function, 
and treelayout function and gplot function could be use to generate 
treeplot function, this construction looks fine, but the
complexity will be higher -  O_time(treeplot) = N (the loop in the while 
loop - rows 61-63 is n*n
now, but I want to improve this patrt to n - this loop will be 
optimalized, and the result will be n :) - I do it as soon as will be 
possible and O_space(treeplot) = M (the Skelet structure) and the 
composition of treelayout and gplot will be  O_time(tp2) = N2, 
O_space(tp2) = M)  so in this way it is better to implement this 
function separately. I think.
</quote>

so perhaps its better to implement it separately.

Regards
David

-- 
David Bateman                                David.Bateman at motorola.com
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