[R-package] change default nrounds to 100 to match LightGBM core library default (#4197)

* use same default arguments as python

* Update R-package/R/lgb.cv.R

Changed.
Co-authored-by: James Lamb <jaylamb20@gmail.com>

* revert change in docs
Co-authored-by: James Lamb <jaylamb20@gmail.com>

R-package/R/lgb.cv.R

@@ -72,7 +72,7 @@ CVBooster <- R6::R6Class(
 #' @export
 lgb.cv <- function(params = list()
                    , data
-                   , nrounds = 10L
+                   , nrounds = 100L
                    , nfold = 3L
                    , label = NULL
                    , weight = NULL

R-package/R/lgb.train.R

@@ -49,7 +49,7 @@
 #' @export
 lgb.train <- function(params = list(),
                       data,
-                      nrounds = 10L,
+                      nrounds = 100L,
                       valids = list(),
                       obj = NULL,
                       eval = NULL,

R-package/R/lightgbm.R

@@ -104,7 +104,7 @@ lightgbm <- function(data,
                      label = NULL,
                      weight = NULL,
                      params = list(),
-                     nrounds = 10L,
+                     nrounds = 100L,
                      verbose = 1L,
                      eval_freq = 1L,
                      early_stopping_rounds = NULL,

R-package/man/lgb.cv.Rd

@@ -7,7 +7,7 @@
 lgb.cv(
   params = list(),
   data,
-  nrounds = 10L,
+  nrounds = 100L,
   nfold = 3L,
   label = NULL,
   weight = NULL,

R-package/man/lgb.train.Rd

@@ -7,7 +7,7 @@
 lgb.train(
   params = list(),
   data,
-  nrounds = 10L,
+  nrounds = 100L,
   valids = list(),
   obj = NULL,
   eval = NULL,

R-package/man/lightgbm.Rd

@@ -9,7 +9,7 @@ lightgbm(
   label = NULL,
   weight = NULL,
   params = list(),
-  nrounds = 10L,
+  nrounds = 100L,
   verbose = 1L,
   eval_freq = 1L,
   early_stopping_rounds = NULL,