Re: Conditional list indexing
- To: mathgroup at smc.vnet.net
- Subject: [mg95915] Re: Conditional list indexing
- From: dh <dh at metrohm.com>
- Date: Thu, 29 Jan 2009 06:00:01 -0500 (EST)
- References: <glpgd4$lha$1@smc.vnet.net>
Hi Daniele,
you could e.g. use:
a = Table[Prime[i], {i, 10}];
b = Select[a, # > 15 &];
Position[a, #] & /@ b // Flatten
hope this helps, Daniel
daniele wrote:
> Hello everybody,
> I'd like to know how I can get the indices of the elements in a list
> that satisfy a certain condition. Here's an example: suppose I have
> the list
>
> a = Table[Prime[i],{i,10}];
>
> that contains {2,3,5,7,11,13,17,19,23,29}.
>
> If I execute the command
>
> b = Select[a,#>15&];
>
> b will contain {17,19,23,29}. I'd like to find a way to obtain a third
> list, say c, that will contain {7,8,9,10}, i.e. the indices of the
> elements in list a that are greater than 15.
>
> Thank you,
> Daniele
>
>