[R] how to search a list that contains multiple dissimilarvectors?

[Eric Rupley]

Gerrit, Eik -- 

Thanks very much for your replies!  This answers my primary question -- was I missing some simple command that did not resort to function() in some manner.  Both are much more streamlined than my 7 line laughable beast of solution.

Best,
Eric



On Mar 28, 2013, at 2:29 AM, Gerrit Eichner wrote:

> Hi, Eric,
> 
> as a quick hack, does
> 
> spots <- sapply( alist,
>                 function( listcomp)
>                  which( listcomp == value.to.look.for) )
> 
> spots[ sapply( spots, length) == 0] <- NULL
> 
> do what you want?
> 
> 
> Regards  --  Gerrit
> 


On Mar 28, 2013, at 2:21 AM, Eik Vettorazzi wrote:

> Hi Eric,
> something like the following might me a starter
> 
> (index<-lapply(alist,function(x)which(x==x.search)))
> 
> cheers.
> 
> Am 28.03.2013 08:40, schrieb Eric Rupley:
>> 
>> Dear All,
>> 
>> This is a simple question, but I'm stumped about the simplest way to search a list object such as the following:
>> 
>> This randomish snippet:
>> 
>> n <- c(round(runif(round(runif(1,1,10),0),1,10),0))
>> alist <- new("list")
>> for (i in seq_along(n)) {
>> 	alist[[i]] <- c(round(runif(round(runif(1,1,10),0),1,10),0))
>> }
>> names(alist) <- sample(letters[1:length(n)])
>> rm(n);c(alist)
>> 
>> 
>> ...produces something like this:
>> 
>> $d
>> [1] 4
>> 
>> $b
>> [1] 3 5 3
>> 
>> $a
>> [1]  2  5  7  3 10  3  4  9  9
>> 
>> $c
>> [1]  6  3  7  4  5 10  8 10  3
>> 
>> My question is how does one search the list for a given value, in a most compressed set of commands, in order two return two separate indices: a) the index of the list element(s) containing the value, and b) the index of the matching value(s) within the vector.
>> 
>> Right now, I'm writing cumbersome loops to iterate though the elements, but there must be a simple, effective method to which I have not found a reference.
>> 
>> Many thanks in advance, and apologies if I have overlooked a reference passage.  
>> Best,
>> Eric
>> 
>> --
>> Eric Rupley
>> University of Michigan, Museum of Anthropology
>> 1109 Geddes Ave, Rm. 4013
>> Ann Arbor, MI 48109-1079
>> 
>> 
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