Rewrote SparkR data manipulation

flightDelayPredictionWithDSVM/Code/sparkDemo/demo.R

@@ -6,12 +6,15 @@
 
 # libraries to use.
 
+if(!require("devtools")) install.packages("devtools")
+devtools::install_github("Microsoft/AzureSMR")
+
+library(AzureSMR)
 library(SparkR)
 library(RevoScaleR)
 library(dplyr)
 library(magrittr)
 library(readr)
-library(AzureSMR)
 library(jsonlite)
 
 # data sources.
@@ -37,6 +40,7 @@ RevoScaleR::rxDataStep(inData=data_xdf_path,
 # initialize spark session.
 
 sc <- SparkR::sparkR.session(
+  master="local[*]",
   sparkPackages="com.databricks:spark-csv_2.10:1.3.0"
 )
 
@@ -61,31 +65,44 @@ sdf_air <- SparkR::read.df(data_parquet_path, source="parquet") # write data int
 
 SparkR::printSchema(sdf_air)
 
-# create a SQL context for manipulating the Spark data frames.
+# filter flights that are not cancelled.
 
-SparkR::createOrReplaceTempView(sdf_air, "air")
-stable_air <-  SparkR::sql("SELECT a.DayofMOnth, a.DayOfWeek, a.Origin, a.Dest, a.DepTime, a.ArrDel15 FROM air a")  
-SparkR::createOrReplaceTempView(stable_air, "stable_air")
+sdf_air <- SparkR::filter(sdf_air, sdf_air$Cancelled == FALSE)
 
-head(SparkR::sql("show tables"))
+# for demonstration purpose, only a few indicators are selected.
 
-# sample 30% data from all.
+sdf_air <- SparkR::select(sdf_air, 
+                          "DayofMonth", 
+                          "DayOfWeek",
+                          "Dest",
+                          "Origin",
+                          "DepTime",
+                          "ArrDel15")
 
-sdf_air_sampled <- SparkR::sample(stable_air,
-                                  withReplacement=FALSE, 
-                                  fraction=0.3,
-                                  seed=123)
+# sample 30% from the data set.
 
-# convert the data into local R data frame for visualization.
+sdf_air <- SparkR::sample(sdf_air, 
+                          FALSE,
+                          0.3)
 
-df_air_sampled <- SparkR::as.data.frame(sdf_air_sampled)
+# summary of the finalized data.
+
+SparkR::collect(describe(sdf_air,
+                         "DayofMonth", 
+                         "DayOfWeek",
+                         "Dest",
+                         "Origin",
+                         "DepTime",
+                         "ArrDel15"))
+
+# convert the data into local R data frame.
+
+df_air_sampled <- SparkR::as.data.frame(sdf_air)
+
+# take a glimpse of the processed data.
 
 dplyr::glimpse(df_air_sampled)
 
-df_air_sampled %<>% 
-  dplyr::filter(as.character(ArrDel15) != "NA") %>%
-  dplyr::mutate(DepTime=as.numeric(DepTime), ArrDel15=as.factor(ArrDel15))
-
 # close Spark session.
 
 SparkR::sparkR.session.stop()