How to tryCatch the same function call multiple times (N times) in R

Question

We have a basic tryCatch that writes a dataframe to Google Sheets, and trys again if the first write fails for any reason:

result = tryCatch({
  print('TRYING')
  googlesheets4::sheet_write(data = our_df, ss = our_spreadsheet, sheet = 'our_sheetname')
}, error = function(e) {
  print('ERROR, TRYING AGAIN')
  googlesheets4::sheet_write(data = our_df, ss = our_spreadsheet, sheet = 'our_sheetname')
})

It is possible to generalize this code to retry the googlesheets4::sheet_write() function call for N number of tries? Is something built into base R for this or is there a good R library that handles unlimited retries of a function?

Answer 1

You can put it in a for loop like this.

First, I am going to define a function that often fails (as I don't have access to your Google sheet).

russian_roulette <- function(n = 6) {
    revolver <- sample(1:n, 1)
    if (revolver == 1) {
        return("You lived")
    } else {
        stop("Better luck next time...")
    }
}

Then you can try it as many times as you consider reasonable. You can replace my call to russian_roulette() with your call to googlesheets4::sheet_write().

NUM_TRIES <- 10

for (i in 1:NUM_TRIES) {
    message(i)
    result <- try({
        russian_roulette()
    })
    if (class(result) != "try-error") {
        print("Success!")
        break
    }
}

Output:

1
Error in russian_roulette() : Better luck next time...
2
Error in russian_roulette() : Better luck next time...
3
Error in russian_roulette() : Better luck next time...
4
Error in russian_roulette() : Better luck next time...
5
Error in russian_roulette() : Better luck next time...
6
[1] "Success!"

result
# [1] "You lived"

I don't know why you expect writing to a file to fail - depending on the reason you may want to add a Sys.sleep() call in there for a certain number of seconds after every failure.