Multiple if conditions in map from purrr

Question

I am trying to create a new character vector in R based on the input value present in 'operator' character vector. The operator variable contains values like ">", "<" "" and NULL. I need to create a new vector like operator_id which has equivalent numeric code for the above mathematical operators. Please find the code that I wrote using for loop. However this is very time consuming and is there any other efficient way of writing this code?

for (ch in operator){
  if (ch == ""){
    #print("hi")
    operator_concept_id = append(operator_concept_id, 4172703L)
    value_as_concept_id = append(value_as_concept_id, 45884084L)
  } else if (ch == ">"){
    #print("hello")
    operator_concept_id = append(operator_concept_id, 4172704L)
    value_as_concept_id = append(value_as_concept_id, 45876384L)
  } else if (ch == "<"){
    #print("less")
    operator_concept_id = append(operator_concept_id, 4171756L)
    value_as_concept_id = append(value_as_concept_id, 45881666L)
  }
  else if(ch== "-"){
    #print("negative")
    operator_concept_id = append(operator_concept_id, 4172703L)
    value_as_concept_id = append(value_as_concept_id, 45878583L)
  } else{
    #print("nothing")
    operator_concept_id = append(operator_concept_id, 0L)
    value_as_concept_id = append(value_as_concept_id, 45881630L)
  }
}

My aim is to create a new output character vector filled with numeric values corresponding to the input(operator) vector which has mathematical symbols. — The Great, Mar 15 '19 at 04:33
What do you mean by corresponding? What is the relationship between the "operator" and values? — NelsonGon, Mar 15 '19 at 04:34
Please take some time reviewing [how to ask](https://stackoverflow.com/help/how-to-ask) questions here on SO, and then provide a [minimal reproducible example/attempt](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example), including sample data. Screenshots of your data/code are never a good idea, as we can't copy&paste from an image. You should provide sample data in a copy&paste-able format (e.g. use `dput`), show your expected output and give a clear reproducible and self-contained problem statement. — Maurits Evers, Mar 15 '19 at 04:34
@NelsonGon - For example , ">" symbol can be represented as 4172704L in numeric form. Similarly "<" can be represented as 4171756L. Numeric form is just another way to represent these symbols which is used in our project. The input vector (operator) has more than 350000 rows and all observations are filled with either "<", ">", NULL "-", etc — The Great, Mar 15 '19 at 04:37

score 2 · Accepted Answer · answered Mar 15 '19 at 04:41

2

Hopefully I got the aim right, this is a possible solution:

Operators<-c(">","<","NULL")#Did not use a real `NULL`
Numerics<-c(1234,567,8910)
purrr::map2(Operators,Numerics,function(x,y) append(x,y))

Result:

#[[1]]
#[1] ">"    "1234"

#[[2]]
#[1] "<"   "567"

#[[3]]
#[1] "NULL" "8910"

answered Mar 15 '19 at 04:41

NelsonGon

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When you have appended it, why is the comma missing between ">" and "1234". Aren't we supposed to see it like ">","1234" which is like 2 items/elements under each index. In that case, I can access them using index positions like [1][2] for example – The Great Mar 15 '19 at 05:10
I was just following your logic. `?append` should provide more details. As far as I know append adds something like a new "column" if this were a `data.frame` object. We could extract like: `purrr::map2(Operators,Numerics,function(x,y) append(x,y))[1][[1]][1]` – NelsonGon Mar 15 '19 at 05:16
can help me with this? https://stackoverflow.com/questions/63370682/unable-to-use-select-map-and-what-does-indicate-in-r – The Great Aug 12 '20 at 06:24

score 1 · Answer 2 · answered Mar 15 '19 at 05:18

We could use a switch statement:

for (ch in operator){
  switch(ch, 
         ">"={
           #print("hello")
           operator_concept_id = append(operator_concept_id, 4172704L)
           value_as_concept_id = append(value_as_concept_id, 45876384L)   
         },
         "<"={
           #print("less")
           operator_concept_id = append(operator_concept_id, 4171756L)
           value_as_concept_id = append(value_as_concept_id, 45881666L)
         },
         "-"={
           #print("negative")
           operator_concept_id = append(operator_concept_id, 4172703L)
           value_as_concept_id = append(value_as_concept_id, 45878583L) 
         },
         {
           #print("hi")
           operator_concept_id = append(operator_concept_id, 4172703L)
           value_as_concept_id = append(value_as_concept_id, 45884084L)
         }
  )

}

Note that we cannot switch on "", instead, I used that as the default option at the end, so anything not fitting the previous cases will execute as that option.

Multiple if conditions in map from purrr

2 Answers2