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Re: Something very simple.....

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87115] Re: [mg87103] Something very simple.....
  • From: "Maarten van der Burgt" <maarten.vanderburgt at icos.be>
  • Date: Tue, 1 Apr 2008 05:18:36 -0500 (EST)

Steve,

Try,

Sphere@@#&/@sphlst

and,

Complement[lsta,lsta[[lstb]]]

maarten



                                                                                                                                                
                    Steve Gray                                                                                                                  
                    <stevebg@roadr        To:     mathgroup at smc.vnet.net                                                                        
                    unner.com>            cc:                                                                                                   
                                          Subject:     [mg87103] Something very simple.....                                                     
                    01/04/2008                                                                                                                  
                    10:19                                                                                                                       
                                                                                                                                                
                                                                                                                                                




1. I have a list of sphere centers and radii like this:

sphlst={{{ 5.11,  0.76, -0.32}, 100.39},
           {{ 7.18, -1.86, -8.19},  98.02},
           {{26.71, -9.30, -6.85}, 111.27},
           {{    0,     0,     0}, 100.00},
           {{ 8.65,  4.28, -3.81}, 103.87}}.

If I do Map[Sphere,sphlst] I get too many braces, like this:

{Sphere[{{ 5.11,  0.76, -0.32}, 100.39}],
 Sphere[{{ 7.18, -1.86, -8.19}, 98.02}],
 Sphere[{{26.71, -9.30, -6.85}, 111.27}],
 Sphere[{{    0,     0,     0}, 100.00}],
 Sphere[{{ 8.65,  4.28, -3.81}, 103.87}]}

and Sphere needs for example Sphere[{1.11, 2.22, 3.33},4.5].
What simple thing am I missing to remove the extra braces?
(I know I can use Table but isn't there a "one-step" method?)
Flatten doesn't seem to be useful here, or I'm using it wrong.

2. I have two lists, lsta={a,b,c,d,e,f} and lstb={1,3,4}.
I want the elements of lsta that do NOT correspond to elements
of lstb, in this case everything from lsta except elements
1,3, and 4: result={b,e,f}.
(lstb won't have entries larger than Length[lsta]).

Thanks for any tips.

Steve Gray







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