CODEWITHSUNDEEP
r
user_newbie10
user_newbie10

Reputation: 163

Using strings from loops as parts of function commands and variable names in R

How does one use the string coming from a loop - to generate new variables
- as a part of functions commands
- as functions' arguments
- as a part of if statements
in R?

Specifically, as an example (the code obviously doesn't work, but I'd like to have something not less intelligible than what is bellow),

list_dist <- c("unif","norm")
for (dist in list_dist){
    paste("rv",dist,sep="") = paste("r",dist,sep="")(100,0,1)
    paste("meanrv",dist,sep="") = mean(paste("rv",dist,sep=""))
    if (round(paste("meanrv",dist,sep=""),3) != 0){
        print("Not small enough")
    }
}

Note: This is an example and I do need to use kind of loops to avoid writing huge scripts.

I managed to use strings as in the example above but only with eval/parse/text/paste and combining the whole statement (i.e. the whole "line") inside paste, instead of pasting only in the varname part or the function part, which makes code ugly and illegible and coding inefficient.

Other available replies to similar questions which I've seen are not specific as in how to deal with this sort of usage of strings from loops.

I'm sure there must be a more efficient and flexible way to deal with this, as there is in some other languages.

Thanks in advance!

Upvotes: 0

Views: 73

Answers (2)

Konrad Rudolph
Konrad Rudolph

Reputation: 545538

Resist the temptation of creating variable names programmatically. Instead, structure your data properly into lists:

list_dist = list(unif = runif, norm = rnorm)
distributions = lapply(list_dist, function (f) f(100, 0, 1))
means = unlist(lapply(distributions, mean))
# … etc.

As you can see, this also gets rid of the loop, by using list functions instead.

Your last step can also be vectorised:

if (any(round(means, 3) != 0))
    warning('not small enough')

Upvotes: 3

cccmir
cccmir

Reputation: 1003

try this:

list_dist <- list(unif = runif,norm = rnorm)
for (i in 1:length(list_dist)){
    assign(paste("rv",names(list_dist)[i],sep=""), list_dist[[i]](100,0,1))
    assign(paste("meanrv",names(list_dist)[i],sep=""),mean(get(paste("rv",names(list_dist)[i],sep=""))))
    if (round(get(paste("meanrv",names(list_dist)[i],sep="")),3) != 0){
        print("Not small enough")
    }
}

Upvotes: 0

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