str2str (version 0.2.1)

try_expr: Add Try to Expression

Description

try_expr evaluates an expression expr and returns a list with three elements: 1) return object, 2) warning message, 3) error message. This can be useful when you want to evaluate an expression and are not sure if it will result in a warning and/or error and don't want R to stop if an error does arise.

Usage

try_expr(expr, output.class = NULL)

Value

list object with three elements: "result" = 1) return object of expr, "warning" = warning message, "error" = error message. When an element is not relevant (e.g., no errors), then that element is NULL.

Arguments

expr

expression

output.class

character vector of length 1 specifying the class you want the returned object of try_expr to be. The default is NULL for no class.

Details

This function is heavily based on the following StackOverflow post: https://stackoverflow.com/questions/4948361/how-do-i-save-warnings-and-errors-as-output-from-a-function.

Examples

# apply to log()
try_expr(log(1))
try_expr(log(0))
try_expr(log(-1))
try_expr(log("a"))
# return a list where NULL if an error or warning appears
lapply(X = list("positive" = 1, "zero" = 0, "negative" = -1,"letter" = "a"),
   FUN = function(x) {
      log_try <- try_expr(log(x))
      result <- log_try[["result"]]
      warning <- log_try[["warning"]]
      error <- log_try[["error"]]
      if (!(is.null(error))) return(NULL)
      if (!(is.null(warning))) return(NULL)
      return(result)
})