improve demo of cv in R

R-package/R/xgb.cv.R

@@ -128,7 +128,7 @@ xgb.cv <- function(params=list(), data, nrounds, nfold, label = NULL, missing =
   for(line in split) dt <- line[2:length(line)] %>% str_extract_all(pattern = "\\d*\\.+\\d*") %>% unlist %>% as.list %>% {vec <- .; rbindlist(list(dt, vec), use.names = F, fill = F)}
   
   if (prediction) {
-    return(list(dt,predictValues))
+    return(list(dt = dt,pred = predictValues))
   }
   return(dt)
 }

R-package/demo/cross_validation.R

@@ -45,3 +45,7 @@ param <- list(max.depth=2,eta=1,silent=1)
 xgb.cv(param, dtrain, nround, nfold = 5,
        obj = logregobj, feval=evalerror)
 
+# do cross validation with prediction values for each fold
+res <- xgb.cv(param, dtrain, nround, nfold=5, prediction = TRUE)
+res$dt
+length(res$pred)