[R] Filling Lists or Arrays of variable dimensions
Jessica Streicher
j.streicher at micromata.de
Fri Dec 21 11:34:06 CET 2012
@David : In my mind it was quite complete enough.
@William: Thanks, didn't know you could do that with data frames, if i ever have to do something similar again i might try this.
On 20.12.2012, at 22:39, David Winsemius wrote:
>
> On Dec 20, 2012, at 10:01 AM, Jessica Streicher wrote:
>
>> Really must have been unclear at some point, sorry.
>
> Hasn't it become abundantly clear that this would have progress farther had you post a complete example?
>
> --
> David.
>>
>> 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-bounces at r-project.org [mailto:r-help-bounces at 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:ccampbell at mango-solutions.com | http://www.mango-solutions.com
>>>>> Mango Solutions
>>>>> 2 Methuen Park
>>>>> Chippenham
>>>>> Wiltshire
>>>>> SN14 OGB
>>>>> UK
>>>>>
>>>>> -----Original Message-----
>>>>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at 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.
>>>>> ______________________________________________
>>>>> R-help at r-project.org mailing list
>>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>>
>>>>> --
>>>>>
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>>>> ______________________________________________
>>>> R-help at r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> David Winsemius
> Alameda, CA, USA
>
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