Create multiple variable, assign attributes, assign values in a for loop

Question

I am looking to create a list of vectors to which I want to assign specific value. I know I can do something like

var_list=c(V1, V2...etc)

Then use var_list[i] in a for loops. To do this thought, I have to manually creates the list at first, which is long. I know I can do something like

for(i in 1:n){
    assign(paste("Mx", i, sep = ""), i)
}

This will creates my variable name. Trouble is, how do I manage them? I would like a way to do something like this :

for(i in 1:n){
    attributes(assign(paste("Mx", i, sep = ""), i))<-list(dim=1:n)
    "here I would like to append the newly created variable (Mx"i") into a list so I could manage the whole thing later on".
}

So I could do :

for (k in 1:n){
for (j in 1:m)
new_list[[k]][j]<-other_list[[k]][(j-1)*3+1]
}

Any1 got a idea? The basic problem is that I have this long list of vector (which is represented here by "other_list"). Each vector in this list has 36 entry. I want to divide each of these vector in three different vector (I need to specify the specific value of the vector from "other_list" I want to apply to the specific value of the vector of the " new_list ". Thanks !

assign is not a function which should be used by beginners. It usually offers only an apparent solution that makes subsequent steps only harder for you. — Roland
– Roland, Commented Mar 23, 2016 at 14:52

Roland · Accepted Answer · 2016-03-23 14:55:57Z

1

Just pre-allocate the list and assign its names:

n <- 10
#pre-allocate list
mylist <- vector(n, mode = "list")
#assign names
names(mylist) <- paste0("Mx", seq_len(n))

#fill the list
for(i in 1:n){
 mylist[[i]] <- i
}

mylist[1:3]
#$Mx1
#[1] 1
#
#$Mx2
#[1] 2
#
#$Mx3
#[1] 3

PS: You should learn to use lapply for such tasks.

setNames(lapply(seq_len(n), identity), paste0("Mx", seq_len(n)))

And the optimal solution for the specific example is this:

setNames(as.list(seq_len(n)), paste0("Mx", seq_len(n)))

edited Mar 23, 2016 at 14:55

answered Mar 23, 2016 at 14:50

Roland

134k12 gold badges203 silver badges305 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

John Over a year ago

Hi, thanks for the answer! I did as you suggested but it did not work at the "assign names" step. When I enter the code " names(mylist)<-paste0("Mx",seq_len(n)) " then run it, it doesn't show any warning message. Then I type in to display "mylist" in the console, and it displays it like this: $<NA> NULL $<NA> NULL

John Over a year ago

... oh well, now it worked... I had erased all the memory thought. Thanks alot :)

Collectives™ on Stack Overflow

Create multiple variable, assign attributes, assign values in a for loop

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related