CODEWITHSUNDEEP
r
JulianS
JulianS

Reputation: 188

Storing numeric vectors in the names of a list

Is it possible to store a numeric vector in the names variable of a list? ie.

x <- c(1.2,3.4,5.9)
alist <- list()
alist[[x]]$somevar <- 2

I know I can store it as a vector within the list element, but I thought it would be faster to move through and find the element of the list I want (or add if needed) if the numeric vector is the name of the list element itself...

EDIT: I have included a snippit of the code in context below, apologies for the change in nomenclature. In brief, I am working on a clustering problem, the dataset is too large to directly do the distance calculation on, my solution was to create bins for each dimension of the data and find the nearest bin for each observation in the original data. Of course, I cannot make a complete permutation matrix since this would be larger than the original data itself. Therefore, I have opted to find the nearest bin for each dimension individually and add it to a vector, temp.bin, which ideally would become the name of the list element in which the rowname of the original observation would be stored. I was hoping that this would simplify searching for and adding bins to the list.

I also realise that the distance calculation part is likely wrong - this is still very much a prototype.

binlist <- list()
for(i in 1:nrow(data)) # iterate through all data points
{
# for each datapoint make a container for the nearest bin found
temp.bin <- vector(length = length(markers))
names(temp.bin) <- markers
for(j in markers) # and dimensions 
{
  # find the nearest bin for marker j
  if(dist == "eucl")
  {
    dists <- apply(X=bin.mat, MARGIN = 1, FUN= function(x,y) {sqrt(sum((x-y)^2))}, y=data[i,j])
    temp.bin[j] <- bin.mat[which(dists == min(dists)),j]
  }
}
### I realise this part doesn't work
binlist[[temp.bin]] <- append(binlist[[temp.bin]], values = i)

The closest answer so far is John Coleman.

Upvotes: 1

Views: 296

Answers (2)

catastrophic-failure
catastrophic-failure

Reputation: 3905

Solution

With some slight modifications we can achieve the following:

x = c(1.2,3.4,5.9)
alist = vector("list", length(x))
names(alist) = x
alist[as.character(x)] = list(c(somevar = 2))
#$`1.2`
#somevar 
#      2 
#
#$`3.4`
#somevar 
#      2 
#
#$`5.9`
#somevar 
#      2

Explanation

Basically:

  • I had to create the list with the correct length (vector("list", length(x)))
  • Then assign the correct names (names(alist) = x)
  • So we can call list levels by name using [ and assign a new list to each list element (alist[as.character(x)] = list(c(somevar = 2)))

2nd Solution

Going by John Coleman comment:

It isn't clear that you answered the question. You gave a list whose vector of names is the the vector x, coerced to character. OP asked if it was possible "if the numeric vector is the name of the list element itself... ". They wanted to treat x as a single name, not a vector of names.

If you wanted to have the list element named after the vector x you could try, using the deparse(substitute(.)) trick

x = c(1.2,3.4,5.9)
alist = list()
alist[[deparse(substitute(x))]]$somevar = 2
#> alist[[deparse(substitute(x))]]
#$somevar
#[1] 2

If you really wanted the numeric values in x as the name itself, then I point you to John's solution.

Upvotes: 1

John Coleman
John Coleman

Reputation: 51998

names(alist) is a character vector. A numeric vector is not a string, hence it isn't a valid name for a list element. What you want is thus impossible. You could create a string representation of such a list and use that as a name, but that would be cumbersome. If this is what you really wanted to do, you could do something like the following:

x <- c(1.2,3.4,5.9)
alist <- list()
alist[[paste(x,collapse = " ")]]$somevar <- 2

This will create a 1-element list whose only element has the name "1.2 3.4 5.9".

While there might be some use cases for this, I suspect that you have an XY problem. What are you trying to achieve?

Upvotes: 2

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