Question

I am trying to use for to create multiple objects from for, just example (not exact):

l_gr <- list (1:10, 11:20, 21:30)
for (i in 1:length(l_gr)){
  grp <- NULL
  grp[[i]] <- mean(l_gr[[i]])
    }

This is not what I am expecting, rather I need to output multiple objects (of different class) however the name is different with i level for example: here grp1, grp2, grp3.
Each of these object has output of the function for particular i list. Sorry for simple question.

Edits: response to provide specific example:

install.packages("onemap")
require(onemap)
data(example.out)
twopts <- rf.2pts(example.out)
all.data <- make.seq(twopts,"all") 
link_gr <- group(all.data)
link_gr$n.groups

starts the loop

  # without loop: 
# for 1
grp1 <- make.seq(link_gr, 1)
grp1.od <- order.seq(input.seq=grp1, n.init = 5,  subset.search = "twopt", 
    twopt.alg = "rcd", THRES = 3, draw.try = TRUE, wait = 1, touchdown=TRUE) 


# for 2
grp2 <- make.seq(link_gr, 2)
grp2.od <- order.seq(input.seq=grp2, n.init = 5,  subset.search = "twopt",  
   twopt.alg = "rcd", THRES = 3, draw.try = TRUE, wait = 1, touchdown=TRUE) 

same process report for 1:1:link_gr$n.groups

So I want create a for loop and output objects:

for (i in 1:link_gr$n.groups){
    grp <- NULL
  grp[i] <- make.seq(link_gr, i)
  grp[i].od <- order.seq(input.seq=grp[i], n.init = 5,  subset.search = "twopt",  
      twopt.alg = "rcd", THRES = 3, draw.try = TRUE, wait = 1, touchdown=TRUE)
    } 

Answer 1

Note that your for loops are wrong. If you set grp <- NULL within the loop, you’ll just wipe your results variable with each iteration – probably not what you want. You need to put the variable initialisation outside the loop.

Note, too, that I’d suggest that you are still better off using a single variable instead of multiple ones. list objects are very flexible in R and can accomodate objects of different classes. You can do

 require(onemap)
 data(example.out)
 twopts <- rf.2pts(example.out)
 all.data <- make.seq(twopts,"all") 
 link_gr <- group(all.data)
 link_gr$n.groups

   # initialise list outputs
 grp = list()
 grp.od = list()
 for (i in 1:2){
 grp[[i]] <- make.seq(link_gr, i)
 grp.od[[i]] <- order.seq(input.seq=grp[[i]], n.init = 5,  subset.search = "twopt", 
     twopt.alg = "rcd", THRES = 3, draw.try = TRUE, wait = 1, touchdown=TRUE) 
 }

 #check out output
 str(grp)
 str(grp.od)
 grp[[1]]
 grp[[2]

If you must insist on using different variables, consider ?assign and ?get. Something like this will work:

 i = 1
 assign(paste("grp", i, sep = ""), grp[[1]])
 exists("grp1")
 str(get(paste("grp", i, sep = "")))