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# | ||
# Licensed to the Apache Software Foundation (ASF) under one or more | ||
# contributor license agreements. See the NOTICE file distributed with | ||
# this work for additional information regarding copyright ownership. | ||
# The ASF licenses this file to You under the Apache License, Version 2.0 | ||
# (the "License"); you may not use this file except in compliance with | ||
# the License. You may obtain a copy of the License at | ||
# | ||
# http://www.apache.org/licenses/LICENSE-2.0 | ||
# | ||
# Unless required by applicable law or agreed to in writing, software | ||
# distributed under the License is distributed on an "AS IS" BASIS, | ||
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
# See the License for the specific language governing permissions and | ||
# limitations under the License. | ||
# | ||
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# For this example, we shall use the "flights" dataset | ||
# The dataset consists of every flight departing Houston in 2011. | ||
# The data set is made up of 227,496 rows x 14 columns. | ||
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# To run this example use | ||
# ./bin/sparkR --packages com.databricks:spark-csv_2.10:1.0.3 | ||
# examples/src/main/r/data-manipulation.R <path_to_csv> | ||
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# Load SparkR library into your R session | ||
library(SparkR) | ||
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args <- commandArgs(trailing = TRUE) | ||
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if (length(args) != 1) { | ||
print("Usage: data-manipulation.R <path-to-flights.csv") | ||
print("The data can be downloaded from: http://s3-us-west-2.amazonaws.com/sparkr-data/flights.csv ") | ||
q("no") | ||
} | ||
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## Initialize SparkContext | ||
sc <- sparkR.init(appName = "SparkR-data-manipulation-example") | ||
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## Initialize SQLContext | ||
sqlContext <- sparkRSQL.init(sc) | ||
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flightsCsvPath <- args[[1]] | ||
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# Create a local R dataframe | ||
flights_df <- read.csv(flightsCsvPath, header = TRUE) | ||
flights_df$date <- as.Date(flights_df$date) | ||
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## Filter flights whose destination is San Francisco and write to a local data frame | ||
SFO_df <- flights_df[flights_df$dest == "SFO", ] | ||
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# Convert the local data frame into a SparkR DataFrame | ||
SFO_DF <- createDataFrame(sqlContext, SFO_df) | ||
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# Directly create a SparkR DataFrame from the source data | ||
flightsDF <- read.df(sqlContext, flightsCsvPath, source = "com.databricks.spark.csv", header = "true") | ||
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# Print the schema of this Spark DataFrame | ||
printSchema(flightsDF) | ||
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# Cache the DataFrame | ||
cache(flightsDF) | ||
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# Print the first 6 rows of the DataFrame | ||
showDF(flightsDF, numRows = 6) ## Or | ||
head(flightsDF) | ||
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# Show the column names in the DataFrame | ||
columns(flightsDF) | ||
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# Show the number of rows in the DataFrame | ||
count(flightsDF) | ||
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# Select specific columns | ||
destDF <- select(flightsDF, "dest", "cancelled") | ||
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# Using SQL to select columns of data | ||
# First, register the flights DataFrame as a table | ||
registerTempTable(flightsDF, "flightsTable") | ||
destDF <- sql(sqlContext, "SELECT dest, cancelled FROM flightsTable") | ||
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# Use collect to create a local R data frame | ||
local_df <- collect(destDF) | ||
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# Print the newly created local data frame | ||
head(local_df) | ||
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# Filter flights whose destination is JFK | ||
jfkDF <- filter(flightsDF, "dest = \"JFK\"") ##OR | ||
jfkDF <- filter(flightsDF, flightsDF$dest == "JFK") | ||
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# If the magrittr library is available, we can use it to | ||
# chain data frame operations | ||
if("magrittr" %in% rownames(installed.packages())) { | ||
library(magrittr) | ||
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# Group the flights by date and then find the average daily delay | ||
# Write the result into a DataFrame | ||
groupBy(flightsDF, flightsDF$date) %>% | ||
summarize(avg(flightsDF$dep_delay), avg(flightsDF$arr_delay)) -> dailyDelayDF | ||
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# Print the computed data frame | ||
head(dailyDelayDF) | ||
} | ||
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# Stop the SparkContext now | ||
sparkR.stop() |
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