Using name of vector argument in function

user_14109040 0
Viewed 64

I am writing a function that passes in a vector of values, and I want to use those values for computation within the function. However, I also want to use the name of the vector that I pass to return meaningful error messages but can not figure out how to do so.

My function looks like this

func <- function(vector, minimumvalue){
    if(length(vector)==1){
      return(1)}
    else if (length(vector)<minimumvalue){
      stop(paste0("The length of vector is less than ",minimumvalue))}
    else if (length(vector)>minimumvalue){
      stop(paste0("The length of vector is more than ",minimumvalue))}
    else (return(vector))
}

My function call looks like this

colours <- c("red","green","blue")
func(colours, 2)

An returns

"The length of vector is more than 2", but I would like to say "The length of colours is more than 2"

I can achieve this by adding another parameter which passes the name of the vector as a string into the function, but I would like to know if there is a better way to design this.

r
2 Answers

I added deparse(substitute(vector)) to get the name of the object as a string.

func <- function(vector, minimumvalue){
  if(length(vector)==1){
    return(1)}
  else if (length(vector)<minimumvalue){
    stop(paste0("The length of ",deparse(substitute(vector))," is less than ",minimumvalue))}
  else if (length(vector)>minimumvalue){
    stop(paste0("The length of ",deparse(substitute(vector))," is more than ",minimumvalue))}
  else (return(vector))
}

colours <- c("red","green","blue")

func(colours, 2)

Error in func(colours, 2) : The length of colours is more than 2

user_96960370

With the glue library, you could format the string easier:

library(glue)
func <- function(vector, minimumvalue){
    if(length(vector)==1){
      return(1)}
    else if (length(vector)<minimumvalue){
      stop(paste0(glue("The length of vector is less than "),minimumvalue))}
    else if (length(vector)>minimumvalue){
      stop(paste0(glue("The length of {substitute(vector)} is more than "),minimumvalue))}
    else (return(vector))
}

colours <- c("red","green","blue")
func(colours, 2)

Output:

Error in func(colours, 2) : 
The length of colours is more than 2

Or even better to use the glue module for formatting minimumvalue as well:

library(glue)
func <- function(vector, minimumvalue){
    if(length(vector)==1){
      return(1)}
    else if (length(vector)<minimumvalue){
      stop(glue("The length of {substitute(vector)} is less than {minimumvalue}"))}
    else if (length(vector)>minimumvalue){
      stop(glue("The length of {substitute(vector)} is more than {minimumvalue}"))}
    else (return(vector))
}

colours <- c("red","green","blue")
func(colours, 2)

The you don't even need paste0.

user_87083640
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