diff --git a/R/classify.R b/R/classify.R
index f15133b..55132b4 100644
--- a/R/classify.R
+++ b/R/classify.R
@@ -42,7 +42,7 @@ monkeylearn_classify <- function(request, key = monkeylearn_key(quiet = TRUE),
   results <- NULL
   headers <- NULL
 
-  for(i in 1:length(request)) {
+  for(i in seq_along(request)) {
 
     if(verbose) {
       message(paste0("Processing request number ", i, " out of ", length(request)))
diff --git a/R/extractor.R b/R/extractor.R
index 71d47da..62c21b3 100644
--- a/R/extractor.R
+++ b/R/extractor.R
@@ -67,7 +67,7 @@ monkeylearn_extract <- function(request, key = monkeylearn_key(quiet = TRUE),
   results <- NULL
   headers <- NULL
 
-  for(i in 1:length(request)) {
+  for(i in seq_along(request)) {
     if(verbose) {
       message(paste0("Processing request number ", i, " out of ", length(request)))
     }
diff --git a/R/utils.R b/R/utils.R
index bc17128..90df3ef 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -52,7 +52,8 @@ monkeylearn_url_extractor <- function(extractor_id) {
 # check text size
 monkeylearn_text_size <- function(request) {
 
-  if(any(unlist(lapply(request, nchar, type = "bytes")) > 500000)) {
+  if(any(unlist(vapply(request, nchar, type = "bytes",
+                       FUN.VALUE = 0)) > 500000)) {
     stop("Each text in the request should be smaller than 500 kb.",
          call. = FALSE)
   }
@@ -98,7 +99,8 @@ monkeylearn_parse <- function(output, request_text) {
                                               digest::digest, algo = "md5",
                                               simplify = TRUE,
                                               USE.NAMES = FALSE),
-                                  unlist(lapply(temp$result, nrow)),
+                                  unlist(vapply(temp$result, nrow,
+                                                FUN.VALUE = 0)),
                                   SIMPLIFY = FALSE))
   } else{
     results <- as.data.frame(temp$result)