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Something very simple.....

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87103] Something very simple.....
  • From: Steve Gray <stevebg at roadrunner.com>
  • Date: Tue, 1 Apr 2008 03:19:45 -0500 (EST)

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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