Generating a new variable every n loops in R

Question

I have a command that generates a variable every 10 loops in R (index1, index2, index3... and so on). The command I have is functional, but I am thinking of a smarter way to write this command. Here's what my command looks like:

for (counter in 1:10){

for (i in 1:100){
if (counter == 1){

index1 <- data1 ## some really long command here, I just changed it to this simple command to illustrate the idea

}

if (counter == 2){

index2 <- data2    
}



.
.
.
# until I reach index10
} indexing closure
} ## counter closure

Is there a way to write this without having to write the conditional if commands? I would like to generate index1, index2.... I am sure there is some easy way to do this but I just cannot think of it.

Thanks.

Answer 1

What you need is the modulo operator %%. inside the inner loop. Ex: 100%%10 returns 0 101%%10 returns 1 92%%10 returns 2 - in other words if it is multiple of 10 then you get 0. And the assign function.

Note: You no longer need the outer loop used in your example. So to create a variable at every 10 iteration do something like this

for(i in 1:100){
#check if i is multiple of 10
   if(i%%10==0){
     myVar<-log(i)
    assign(paste("index",i/10,sep=""), myVar)
   }

}


ls() #shows that index1, index2, ...index10 objects have been created.
index1 #returns 2.302585

update: Alternatively, you can store results in a vector

  index<-vector(length=10)
        for(i in 1:100){
        #check if i is multiple of 10
           if(i%%10==0){
             index[i/10]<-log(i)
           }

        }
index #returns a vector with 10 elements, each a result at end of an iteration that is a multiple of 10.