Add index keys to a vector or data frame or list or matrix

Index a vector or lists and convert to a list of objects

Usage

add_key(vector)

Arguments

vector

vector or data frame to transform

Value

a transformed list containing keys along with vector values

Details

This function takes a vector and turns it into a list containing 'key' and 'value' for each vector. This allows the output to be used in loops such as for loops or lapply or other functions to track the index of the list content e.g. 1,2,3...

This function also contains a validator to ensure that a vector had not been previously 'keyed', which prevents the user from inadvertently calling the function twice on a vector. Helps especially because the function keys the vector, and sets the new list to the variable name of the original vector.

Use case

Efficient for loops and for tracking various steps through a vector contents

Examples

#ex1 simple conversion of a vector
rti2 <- c("rpkg","obinna", "obianom")
add_key(rti2)
rti2
#> [[1]]
#> [[1]]$key
#> [1] 1
#> 
#> [[1]]$value
#> [1] "rpkg"
#> 
#> 
#> [[2]]
#> [[2]]$key
#> [1] 2
#> 
#> [[2]]$value
#> [1] "obinna"
#> 
#> 
#> [[3]]
#> [[3]]$key
#> [1] 3
#> 
#> [[3]]$value
#> [1] "obianom"
#> 
#> 
#> attr(,"class")
#> [1] "klist" "list" 

#ex2 add keys to a vector content for use in downstream processes
ver1 <- c("Test 1","Test 2","Test 3")
add_key(ver1)

#ex3 use keyed ver1 in for loop
for(i in ver1){
  message(sprintf("%s is the key for this %s", i$key, i$value))
}
#> 1 is the key for this Test 1
#> 2 is the key for this Test 2
#> 3 is the key for this Test 3

#ex4 use keyed ver1 in lapply loop
xl1 <- lapply(ver1,function(i){
  message(sprintf("lapply - %s is the key for this %s", i$key, i$value))
})
#> lapply - 1 is the key for this Test 1
#> lapply - 2 is the key for this Test 2
#> lapply - 3 is the key for this Test 3