Really must have been unclear at some point, sorry.
William, thats interesting, but not really helping the main problem, which is:
how to do
> l[[ as.character(grid[1, ]) ]] <- 1
without having initialized the list in the loop before.
Well, or how to initialize it without having to do the loop thing, because the
loop stuff can only be done for a specific set of parameter vectors. But those
change, and i don't want to have to write another loop construct every time for
the new version.
I want to say: hey, i have these vectors here with these values (my
parameters), could you build me that nested list structure (tree - whatever)
from it? And the function will give me that structure whatever i give it
without me needing to intervene in form of changing the code.
-------------- Clarification -----------------
First: i am not computing statistics over the parameters. I'm computing stuff
from other data, and the computation is affected by the parameters.
I am computing classifiers for different sets of parameters for those
classifiers. So the result of doSomething() isn't a simple value. Its usually a
list of 6 lists (doing cross validation), which in turn have the classifier
object, some statistics of the classifier (e.g what was missclassified), and
the subsets of data used in them.
That doesn't really fit in a data.frame, hence the use of lists. I want the
nested lists because it helps me find stuff in the object browser faster, and
because all my other code is already geared towards it. If i had the time i
might still go for a flat structure that everyone keeps telling me to use (got
a few mails off the list),
but i really haven't the time.
If theres no good way i'll just keep things as they are now.
On 20.12.2012, at 18:37, William Dunlap wrote:
> Arranging data as a list of lists of lists of lists [...] of scalar values
> generally
> will lead to slow and hard-to-read R code, mainly because R is designed to
> work on long vectors of simple data. If you were to start over, consider
> constructing
> a data.frame with one column for each attribute. Then tools like aggregate
> and
> the plyr functions would be useful.
>
> However, your immediate problem may be solved by creating your 'grid' object
> as a data.frame of character, not factor, columns because as.character works
> differently
> on lists of scalar factors and lists of scalar characters. Usually
> as.<mode>(x), when
> x is a list of length-1 items, gives the same result as as.<mode>(unlist(x)),
> but not when
> x is a list of length-1 factors:
>
>> height<-c("high", "low")
>> width<-c("slim", "wide")
>> gridF <- expand.grid(height, width, stringsAsFactors=FALSE)
>> gridT <- expand.grid(height, width, stringsAsFactors=TRUE)
>> as.character(gridF[1,])
> [1] "high" "slim"
>> as.character(gridT[1,])
> [1] "1" "1"
>> as.character(unlist(gridT[1,])) # another workaround
> [1] "high" "slim"
>
> Your example was not self-contained so I changed the call to doSomething() to
> paste(h,w,sep="/"):
>
> height<-c("high", "low")
> width<-c("slim", "wide")
>
> l <- list()
> for(h in height){
> l[[h]] <- list()
> for(w in width){
> l[[h]][[w]] <- paste(h, w, sep="/") # doSomething()
> }
> }
>
> grid <- expand.grid(height, width, stringsAsFactors=FALSE)
> as.character(grid[1,])
> # [1] "high" "slim", not the [1] "1" "1" you get with stringsAsFactors=TRUE
> l[[ as.character(grid[1, ]) ]]
> # [1] "high/slim"
> l[[ as.character(grid[1, ]) ]] <- 1
> l[[ as.character(grid[1, ]) ]]
> # [1] 1
>
> Bill Dunlap
> Spotfire, TIBCO Software
> wdunlap tibco.com
>
>> -----Original Message-----
>> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
>> Behalf
>> Of Jessica Streicher
>> Sent: Thursday, December 20, 2012 8:43 AM
>> To: Chris Campbell
>> Cc: R help
>> Subject: Re: [R] Filling Lists or Arrays of variable dimensions
>>
>> Aggregate is highly confusing (and i would have appreciated if you used my
>> example
>> instead, i don't get it to do anything sensible on my stuff).
>>
>> And this seems not what i asked for anyway. This may be a named list but not
>> named and
>> structured as i want it at all.
>>
>> happy Christmas too
>>
>> On 20.12.2012, at 15:48, Chris Campbell wrote:
>>
>>> Dear Jessica
>>>
>>> Aggregate is a function that allows you to perform loops across multiple
>>> variables.
>>>
>>> tempData <- data.frame(height = rnorm(20, 100, 10),
>>> width = rnorm(20, 50, 5),
>>> par1 = rnorm(20))
>>>
>>> tempData$htfac <- cut(tempData$height, c(0, 100, 200))
>>> tempData$wdfac <- cut(tempData$width, c(0, 50, 100))
>>>
>>> doSomething <- function(x) { mean(x) }
>>>
>>> out <- aggregate(tempData["par1"], tempData[c("htfac", "wdfac")],
>>> doSomething)
>>>
>>> # out is a data frame; this is a named list.
>>> # use as.list to remove the data.frame class
>>>
>>>> as.list(out)
>>>
>>> $htfac
>>> [1] (0,100] (100,200] (0,100] (100,200]
>>> Levels: (0,100] (100,200]
>>>
>>> $wdfac
>>> [1] (0,50] (0,50] (50,100] (50,100]
>>> Levels: (0,50] (50,100]
>>>
>>> $par1
>>> [1] -1.0449563 -0.3782483 -0.9319105 0.8837459
>>>
>>>
>>
>>>
>>> I believe you are seeing an error similar to this one:
>>>
>>>> out[[1:3]] <- 1
>>> Error in `[[<-`(`*tmp*`, i, value = value) :
>>> recursive indexing failed at level 2
>>>
>>> This is because double square brackets for lists can only set a single list
>>> element at
>> once; grid[1, ] is longer.
>>
>>>
>>> Happy Christmas
>>>
>>> Chris
>>>
>>>
>>> Chris Campbell
>>> Tel. +44 (0) 1249 705 450 | Mobile. +44 (0) 7929 628 349
>>> mailto:ccampb...@mango-solutions.com | http://www.mango-solutions.com
>>> Mango Solutions
>>> 2 Methuen Park
>>> Chippenham
>>> Wiltshire
>>> SN14 OGB
>>> UK
>>>
>>> -----Original Message-----
>>> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
>>> Behalf
>> Of Jessica Streicher
>>> Sent: 20 December 2012 12:46
>>> To: R help
>>> Subject: [R] Filling Lists or Arrays of variable dimensions
>>>
>>> Following problem:
>>>
>>> Say you have a bunch of parameters and want to produce results for all
>>> combinations
>> of those:
>>>
>>> height<-c("high","low")
>>> width<-c("slim","wide")
>>>
>>> then what i used to do was something like this:
>>>
>>> l<-list()
>>> for(h in height){
>>> l[[h]]<-list()
>>> for(w in width){
>>> l[[h]][[w]] <- doSomething()
>>> }
>>> }
>>>
>>> Now those parameters aren't always the same. Their number can change and the
>> number of entries can change, and i'd like to have one code that can handle
>> all
>> configurations.
>>>
>>> Now i thought i could use expand.grid() to get all configurations ,and than
>>> iterate over
>> the rows, but the problem then is that i cannot set the values in the list
>> like above.
>>>
>>> grid<-expand.grid(height,width)
>>> l[[as.character(grid[1,])]] <-1
>>> Error in `[[<-`(`*tmp*`, as.character(grid[1, ]), value = 1) :
>>> no such index at level 1
>>>
>>> This will only work if the "path" for that is already existent, and i'm not
>>> sure how to
>> build that in this scenario.
>>>
>>> I then went on and built an array instead lists of lists, but that doesn't
>>> help either
>> because i can't access the array with what i have in the grids row - or at
>> least i don't
>> know how.
>>>
>>> Any ideas?
>>>
>>> I'd prefer to keep the named lists since all other code is built towards
>>> this.
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