CODEWITHSUNDEEP
rcharacter
David Lee
David Lee

Reputation: 127

Assign a value to character named variable with index

I know we can use assign to assign values to a character name vector. For example

assign("target",1:5)

However, if we want to change the 1st element of the target(target can be a vector/matrix/list), how should we do that? target here can also be a matrix, so we can change one element, one row or one column. I want to do something like

target[1] <- 99

if I use

assign("target[1]",99)

it will only generate a new object named target[1] and value is 99. Here is a simple and trial example

# This function is meaningless, just used to show my situation
# variable_name is a character
example_function <- function(variable_name){
    assign(variable_name,1:5)

    if(rnorm(1)>1){
    variable_name[1] <- 99 #This will not work and I just need some function to achive this purpose
    }
}
example_function("justAname")

Upvotes: 0

Views: 1764

Answers (1)

jamieRowen
jamieRowen

Reputation: 1549

As an alternative approach you could use the [<- function.

f = function(variable_name){
  assign(variable_name,1:5)
  if(rnorm(1)>1){
    `[<-`(eval(as.name(variable_name)),i = 1, value = 99)
  }
  get(variable_name)
}

This should also work with matrices

f_mat = function(variable_name){
  assign(variable_name,matrix(1:25,nrow = 5))
  if(rnorm(1)>1){
    `[<-`(eval(as.name(variable_name)),i = 1, j = , value = 99) # for 1st row
    # `[<-`(eval(as.name(variable_name)),i = , j = 1, value = 99) # for 1st col
    #specify i and j for ith row jth column
  }
  get(variable_name)
}

and lists similarly.

Upvotes: 1

Related Questions