Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1996
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1996

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

Search the Archive

Re: patterns

  • To: mathgroup at smc.vnet.net
  • Subject: [mg3744] Re: patterns
  • From: gaylord at ux1.cso.uiuc.edu (richard j. gaylord)
  • Date: Sun, 14 Apr 1996 03:01:30 -0400
  • Organization: university of illinois
  • Sender: owner-wri-mathgroup at wolfram.com

In article <4kkth9$7jl at dragonfly.wolfram.com>, ianc at wolfram.com (Ian
Collier) wrote:

> In article <4ki9uv$9dm at dragonfly.wolfram.com>, Susan Rempe
> <rempe at euclid.chem.washington.edu> wrote:
> 
> > I have a list of numbers and symbols.
> > How can I collect all the members of the list
> > which have a common denominator?
> > 
> > ex.  list={Sin[theta]/r, Cos[theta]/(r*s), 2*Csc[theta]/(2*r)}
> > 
> >  Say I want to collect all members of the list with r in the denominator;
> > 
> >  i.e.  answer=Sin[theta]/r;
> > 
> 
> 
> If you know exactly what the denominator you want to select is then the
> folling will work:
> 
> 
> In[19]:=
>     list={Sin[theta]/r, Cos[theta]/(r*s), 2*Csc[theta]/(2*r)}
> Out[19]=
>      Sin[theta]  Cos[theta]  Csc[theta]
>     {----------, ----------, ----------}
>          r          r s          r
> 
> In[20]:=
>     ?Select
> 
>     Select[list, crit] picks out all elements ei of list for
>        which crit[ei] is True. Select[list, crit, n] picks out
>        the first n elements for which crit[ei] is True.
> 
> In[21]:=
>     Select[ list, Denominator[ # ]==r&]
> Out[21]=
>      Sin[theta]  Csc[theta]
>     {----------, ----------}
>          r           r
> 


ian [and the others who have posted responses to this question]:

you've all apparently missed the point of what this person wants to do [i
think]. she wants ONLY Sin[theta]/r to be returned, not 2*Csc[theta]/(2*r)
as well. 

i'd give the answer to this question, myself but there is too little room
in the margin to fit it in.


-fermat-

-- 
"if you're not programming functionally, then you're programming dysfunctionally"

==== [MESSAGE SEPARATOR] ====


  • Prev by Date: Re: Power Mac printing bug
  • Next by Date: Re: patterns
  • Previous by thread: Re: patterns
  • Next by thread: Re: patterns