Re: Something very simple.....

• To: mathgroup at smc.vnet.net
• Subject: [mg87116] Re: Something very simple.....
• From: dh <dh at metrohm.ch>
• Date: Tue, 1 Apr 2008 05:18:47 -0500 (EST)
• References: <fssr6s\$biu\$1@smc.vnet.net>

Hi Steve,

1) you must use Map together with Apply:

Map[Sphere@@#&,sphlst]

2) here we the complement of the indices and then use Part:

lsta[[ Complement[Range[Length[lsta]],lstb]] ]

hope this helps, Daniel

Steve Gray wrote:

> 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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