[Date Index]
[Thread Index]
[Author Index]
Re: Using Select within Map
*To*: mathgroup at smc.vnet.net
*Subject*: [mg71799] Re: Using Select within Map
*From*: dh <dh at metrohm.ch>
*Date*: Wed, 29 Nov 2006 02:56:49 -0500 (EST)
*Organization*: hispeed.ch
*References*: <ekh70s$s7p$1@smc.vnet.net>
Hi Mark,
Mathematica is clever enough to figure where an argument belongs if this
is possible. E.g.:
Map[2 # &, Select[{a, b, c, a}, (# == a || # == b) &]]
Of course, if you e.g. multiply arguments of different functions, there
is no way Mathematica could know which argument belongs to which function.
If the # notation does not work, there is still the notation:
Function[x,..] that works with named arguments.
Daniel
Mark Teagarden wrote:
> Hi,
>
> I have a data set which comprises several paired lists, like so (I apologize
> if the tabs do not come out correctly in your mail client):
>
> x =
> {
> {
> { , },
> { , },
> { , }
> },
> {
> { , },
> { , },
> { , }
> },
> {
> { , },
> { , },
> { , }
> }
> }
>
> What I would like to do is to select from each of those paired lists, only
> those pairs where the first value in the pair falls within some specified
> range, and then obtain a mean. This would be simple enough if I was
> operating on a single paired list, for example:
>
> Select[x[[1]],a < #[[1]] < b&]
>
> However, I would like to Map over x so that I would end up with means for
> each of the level 1 lists within x; therein lies the problem. Both Map and
> Select use the Slot operator (#), and I don't know how to distinguish
> between the slot operator used by Map, and the slot operator used by Select:
>
> Select[#,a < #[[1]] < b&]/@x
>
> Or if you prefer:
>
> Map[Select[#, a < #[[1]] < b&,x]
>
> This problem has been plaguing me for some time, and if I could punch
> through it I would be very happy indeed. Any ideas? I have had no luck
> looking through the archives or the Help Browser. On a similar note, I
> would eventually like to modify this solution so that the criteria, a and b,
> could vary with each level 1 list in x, but one thing at a time...
>
> Thanks in advance,
> Mark
>
Prev by Date:
**Re: Using Select within Map**
Next by Date:
**Re: Using Select within Map**
Previous by thread:
**Re: Using Select within Map**
Next by thread:
**Re: Using Select within Map**
| |