[R] Odp: create an object in a loop (v2)

[Petr PIKAL]

Hi

I would recommend to create a dummy object of class list with names 

vvv<-vector("list", 5)
> vvv
[[1]]
NULL

[[2]]
NULL

[[3]]
NULL
...
names(vvv)<-paste(letters[1:5], "_", 1:5, "_some.thing", sep="")
vvv
$a_1_some.thing
NULL

$b_2_some.thing
NULL

$c_3_some.thing
NULL
...

Than you can call your list according to name or according to number

for (i in 1:5) vvv[[i]] <- some.procedure

But I am not sure if it suits your purpose.

Regards
Petr
 


r-help-bounces at r-project.org napsal dne 01.02.2010 16:45:16:

> Hi everybody,
> 
> I'm kind of surprised that I didn't get any answer to my question... Is 
> it not interesting? Is it not well explained? Am I doing something 
> wrong? Was it lost in the hundreds of other emails during the weekend?
> 
> I hope it is because of my last guess. So I'll just send the email again 

> (see below).
> I really need some help on this matter.
> 
> Thanks in advance.
> 
> > To run some statistical tests from the package WRS (from Rand R 
> > Wilcox), I need to store my data in a list, which fac2list() from this 

> > package does very well.
> > But I would like to do it in a loop for each numerical variable. It 
> > would be easier!
> >
> > For now, I have the loop with the extraction and storage into a list. 
> > The code is below.
> > -----
> > # Defines variables
> > file <- ssfamed                          #data file object to be used
> > spec <- "cotau"                         #species selection
> > bone <- "tx"                              #tooth row selection
> > cat <- 3                                    #column indexe to be used 
> > as categorical variable
> > seq.num <- c(seq(7,21,1))        #column indexes to be used as 
> > numerical variables
> >
> > # Select data for species and tooth row
> > select <- file[file$SPECSHOR==spec & file$BONE==bone, ]
> >
> > #Separate the data from each numeric variable in seq.num (select[,k]) 
> > into groups from levels in select[cat] and store into list mode.
> > for(i in 1:length(seq.num)) {
> >  k <- seq.num[i]
> >  name.num <- names(file)[k]
> >  TO_POS_Asfc.median_cotautx <- fac2list(select[,k], select[cat])
> >  names(TO_POS_Asfc.median_cotautx) <- levels(factor(select[[cat]]))
> > }
> > -----
> >
> > What I want to do is, instead of giving manually the name of the list 
> > (here TO_POS_Asfc.median_cotautx), I would like the name of the list 
> > to be created in the loop too, so that it looks like: 
> > select[[cat]]_name.num_specbone. In the code it would look like:
> > -----
> > select[[cat]]_name.num_specbone <- fac2list(select[,k], select[cat]) 
> > #create the list from the values of these variables at each iteration 
> > of the loop
> > names(select[[cat]]_name.num_specbone) <- 
levels(factor(select[[cat]]))
> > -----
> > I thought about using paste(), but I cannot create an object like 
this.
> > In my small R life, I've always stored data into pre-defined objects, 
> > I have no idea how to create an object automatically within a loop.
> >
> > Is my question clear? I hope so. I thought there might be a function 
> > that would create an object where the name would come from a string 
> > stored in an other object.
> >
> > Why do I want that? Simply because I want to run several statistical 
> > tests on each list and I would therefore like to have standardized 
> > names for the data objects.
> >
> > There might be easier ways to do what I want to, I'm open to all 
> > suggestions but I would prefer to stay close from my idea (I would 
> > understand better!)
> 
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