Handle errors with tryCatch

Brief explanation

• See how a for loop and a purrr::map function work with an input whose elements are problematic.
  
• For more information, visit an Advanced R webpage.

Workflow

• Step 1: Load a library to your R session.

library(tidyverse)

• Step 2: Define a function that handles errors.

test_function <- function(x){
  tryCatch(
    log(x),                           # your function body 
    error = function(c){return(NA)}   # action you want to see if an error occurs 
  )
}

• Step 3: Define a list whose elements vary from numeric, character, negative integer, zero, to missing.

test_list <- list(5, "a", -1, 0, NA)

• Step 4: Run a for loop to see if it works with problematic list elements.

output <- for (i in 1:5){
  log(test_list[[i]])
}
output 
# Error in log(test_list[[i]]) : 
#   non-numeric argument to mathematical function

• Step 5: Create a list with log and test_function.

map(test_list, log)
# Error in .Primitive("log")(x, base) : non-numeric argument to mathematical function

map(test_list, test_function)

## Warning in log(x): NaNs produced

## [[1]]
## [1] 1.609438
## 
## [[2]]
## [1] NA
## 
## [[3]]
## [1] NaN
## 
## [[4]]
## [1] -Inf
## 
## [[5]]
## [1] NA

• Step 6: Create a numeric vector with log and test_function.

map_dbl(test_list, log)  
# Error in .Primitive("log")(x, base) : non-numeric argument to mathematical function

map_dbl(test_list, test_function)

## Warning in log(x): NaNs produced

## [1] 1.609438       NA      NaN     -Inf       NA