CODEWITHSUNDEEP
arraysrstringfunction
Doğuş
Doğuş

Reputation: 1957

if==True;but built-in functions doesn't run

f <- readLines('/home/dogus/Desktop/phonezzzz/vcards.txt', encoding="UTF-8")

#empty lists
names <- c()
numbers <- c()

phonezz <- function(){

  for(i in 1:length(f)){

    if("FN" == substring(f[i],0,2)){
    name <- substring(f[i],4)  # doesn't run
    number <- substring(f[i+1],10) # doesn't run

    names <- c(names, name) # doesn't run ; append 'name' into the 'names' list
    numbers <- c(numbers, number) # doesn't run
    print("Hello World")}

    else{
    print("------") 
    next
      }
  }
}
phonezz()
names

Here is the gist link: https://gist.github.com/dgsbicak/b9e2d4fb1dbb70c964295ef88120f404

I use R Studio.

When I run this script, in Global Environment section it shows:

Values:

f           chr[1:3000] "some string" "some string2" "FN:213123123123" ...
names       NULL (empty)
numbers     NULL (empty)

Functions:

phonezz     function ()

So name and number variables are not even exists; names list shows an empty list. And as I said it returns lots of "Hello World". So I dont understand what is the problem?

Kind Regards,

EDIT:

f <- readLines('/home/dogus/Desktop/phonezzzz/vcards.txt', encoding="UTF-8")

names <- c()
numbers <- c()

phonezz <- function() {for(i in 1:length(f))
  {
    if("FN" == substring(f[i],0,2)){
      name <<- substring(f[i],4)
      number <<- substring(f[i+1],10)
      names <<- c(names, name)
      numbers <<- c(numbers, number)
      print("Hello World")
      return(list(names, numbers))
    }
    else{
      print("------")
      next
    }
  }
}
phone <- phonezz()
phone

Now the result is:

Values:

f         chr[1:3089] "asdasd" "asdasd" ...
name      "just last person's name"
number    "just last person's number"

names     "just last person's name in the list"
numbers   "just last person's number in the list"
phone     List of 2

Functions:

phonezz   function ()

Upvotes: 0

Views: 53

Answers (2)

IRTFM
IRTFM

Reputation: 263411

This does not create a list:

numbers <- c()

Proof:

is.list(c())
[1] FALSE

Use instead:

my.names <- list()   #don't use `names` ... it's the name of a function
numbers <- list()

Then another problem is that a for-loop does not return anything (except, it does return NULL, but that's rarely useful). It only operates in the local environment of your function. A further (minor) problem is that indexing in R starts at 1 (NOT 0) so substring(f[i],0,2) probably doesn't really make sense. If you had commented your code, we might know if you wanted 2 or 3 letters. I'm guessing 2, since you compare to "FN". Use substring(f[i],1,2). And then look at:

 substring("string", 4)
[1] "ing"  # so it returns the entire "tail" of the the input character value

Then there is a further problem that your for-loop is overwriting EVERY value. So you should not be surprised if you only get one set of values. You need to index items inside the for-loop and then OUTSIDE the loop you need to additionally apply the return operation. The <<- is only going to push those values one level "up" which is still inside the function environment. Nothing is going to happen outside.

If you had a complete example we could deliver a worked solution but I think this should help you understand the several problems that are immediately visible in your effort to start learning R. See [MCVE] and "how to make a great reproducible example in R"

Upvotes: 1

Kevin
Kevin

Reputation: 339

The variables names and numbers do not exist outside of the function phonezz() Add the return(list(names, numbers) as suggested above. Then call the function as test_list <- phonezz(). The variable test_list should contain the names and numbers.

Upvotes: 1

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