need to assign variables some values in a loop in R

Question

I need to assign variables some values in a loop

Eg:

abc_1<-  
abc_2<-
abc_3<-
.....

something like:

for(i in 1:20)
{
 paste("abc",i,sep="_")<-some calculated value
}

I have tried to use paste as above but it doesn't work. How could this be done.Thanks

Don't name your variables like this. You'll be better off placing values in a list or vector. — MrFlick
– MrFlick, Commented Feb 12, 2015 at 6:29

Steve Bronder · Accepted Answer · 2015-02-12 07:12:22Z

2

assign() and paste0() should help you.

for example:

object_names <- paste0("abc",1:20)

for (i in 1:20){
   assign(object_names[i],runif(40))
}

assign() takes the string in object_names and assigns the function in the second argument to each name. When you place a numeric vector inside of paste0() it gives back a character vector of concatenated values for each value in the numeric vector.

edit:

As Gregor says below, this is much better to do in a list because:

It will be faster.
When making a large number of things you probably want to do the same thing to each of them. lapply() is very good at this.

For example:

N <- 20
# create random numbers in list
abcs <- lapply(1:N,function(i) runif(40))
# multiply each vector in list by 10
abc.mult <- lapply(1:length(abcs), function(i) abcs[[i]] * 10)

edited Feb 12, 2015 at 7:12

answered Feb 12, 2015 at 6:37

Steve Bronder

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1 Comment

Steve Bronder Over a year ago

Your 100% right, but the question asked for creating objects so I gave him an answer. stuff <- lapply(1:length(N),runif(10)) would be much quicker.

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