How to use "tryCatch" to skip errors in a nested loop in R?

Question

I am trying to load a few data with a nested-loop using pageviews. You already helped me get this result:

library("pageviews")

lang = c("it.wikipedia")
bm = c("ECB","Christine Lagarde")

x <- list(
    list(),
    list(),
    list(),
    list(),
    list()
    ) # store results

for (i in seq_along(lang)) {
  for (j in seq_along(bm)) {
        
x[[i]][[j]] = article_pageviews(project = lang[i], article = bm[j], platform = "all", user_type = "user", start = "2015100100", end = today(), reformat = TRUE, granularity = "daily")
  
  }
}

The last step I need to do, however, involves reading some article for which project doesn't exist. Find an example below:

lang = c("it.wikipedia")
bm = c("Philip Lane")

    
x = article_pageviews(project = lang, article = bm, platform = "all", user_type = "user", start = "2015100100", end = today(), reformat = TRUE, granularity = "daily")
 
# Error in FUN(X[[i]], ...) : 
#  The date(s) you used are valid, but we either do not have data for those date(s), or the project you asked for is not loaded yet.  Please check https://wikimedia.org/api/rest_v1/?doc for more information.

I would like to add this to the loop. I tried a few solutions but I don't manage to make the loop skip over if there is an error. I post below one mistaken attempt:

lang = c("it.wikipedia")
bm = c("ECB", "Christine Lagarde", "Philip Lane")

for (i in seq_along(lang)) {
  for (j in seq_along(bm)) {
    
  skip_to_next <- FALSE
    
  tryCatch(x[[i]][[j]] = article_pageviews(project = lang[i], article = bm[j], platform = "all", user_type = "user", start = "2015100100", end = today(), reformat = TRUE, granularity = "daily"), error = function(e) {skip_to_next <<- TRUE})
  
    if(skip_to_next) { next }     

  }
}

Can anyone help me run the loop and skip whenever it meets an error?

Thanks a lot!

Ronak Shah · Accepted Answer · 2021-03-19 13:57:39Z

1

You can use tryCatch as :

library(pageviews)
library(purrr)

lang = c("it.wikipedia")
bm = c("ECB", "Christine Lagarde", "Philip Lane")

map_df(lang, function(x) map_df(bm, function(y) 
  tryCatch(article_pageviews(project = x, article = y, platform = "all", user_type = "user", start = "2015100100", end = today(), reformat = TRUE, granularity = "daily"), 
           error = function(e) {}))) -> result

answered Mar 19, 2021 at 13:57

Ronak Shah

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