Name list elements based on variable names R

Question

I want to add elements to an empty list on the fly. Each element in the list should be named automatically after a set of variables which value will vary.

However,

Answer 1

You cannot assign to paste() using the <- operator (and I believe this is true for the eval() function as well). Instead, you need to either use the [[ operator or use the names() function. You can do this like so:

L <- list()
var1 <- "wood"
var2 <- 1.0
var3 <- "z4"
varname <- paste(var1, as.character(var2), var3, sep="_")

# Using [[
L[[varname]] <- c(0,1)

> L
$wood_1_z4
[1] 0 1

# Using names()
L[[1]] <- c(0,1)
names(L)[1] <- varname

> L
$wood_1_z4
[1] 0 1

A more effective way to do this might be to use a function that both creates the value and names the list element, or even one that just creates the value - if you then use sapply you can name each list element using arguments from the call to your function and the USE.NAMES options.

In a general sense, R isn't really well-optimized for growing lists over time when the final size and structure of the list aren't well-known. While it can be done, a more "R-ish" way to do it would be to figure out the structure ahead of time.