df <- as.DataFrame(faithful)

# Displays the first part of the SparkDataFrame
head(df)
##  eruptions waiting
##1     3.600      79
##2     1.800      54
##3     3.333      74

sparkR.session(sparkPackages = "org.apache.spark:spark-avro_2.12:3.5.1")

people <- read.df("./examples/src/main/resources/people.json", "json")
head(people)
##  age    name
##1  NA Michael
##2  30    Andy
##3  19  Justin

# SparkR automatically infers the schema from the JSON file
printSchema(people)
# root
#  |-- age: long (nullable = true)
#  |-- name: string (nullable = true)

# Similarly, multiple files can be read with read.json
people <- read.json(c("./examples/src/main/resources/people.json", "./examples/src/main/resources/people2.json"))

df <- read.df(csvPath, "csv", header = "true", inferSchema = "true", na.strings = "NA")

write.df(people, path = "people.parquet", source = "parquet", mode = "overwrite")

sparkR.session()

sql("CREATE TABLE IF NOT EXISTS src (key INT, value STRING)")
sql("LOAD DATA LOCAL INPATH 'examples/src/main/resources/kv1.txt' INTO TABLE src")

# Queries can be expressed in HiveQL.
results <- sql("FROM src SELECT key, value")

# results is now a SparkDataFrame
head(results)
##  key   value
## 1 238 val_238
## 2  86  val_86
## 3 311 val_311

# Create the SparkDataFrame
df <- as.DataFrame(faithful)

# Get basic information about the SparkDataFrame
df
## SparkDataFrame[eruptions:double, waiting:double]

# Select only the "eruptions" column
head(select(df, df$eruptions))
##  eruptions
##1     3.600
##2     1.800
##3     3.333

# You can also pass in column name as strings
head(select(df, "eruptions"))

# Filter the SparkDataFrame to only retain rows with wait times shorter than 50 mins
head(filter(df, df$waiting < 50))
##  eruptions waiting
##1     1.750      47
##2     1.750      47
##3     1.867      48

# We use the `n` operator to count the number of times each waiting time appears
head(summarize(groupBy(df, df$waiting), count = n(df$waiting)))
##  waiting count
##1      70     4
##2      67     1
##3      69     2

# We can also sort the output from the aggregation to get the most common waiting times
waiting_counts <- summarize(groupBy(df, df$waiting), count = n(df$waiting))
head(arrange(waiting_counts, desc(waiting_counts$count)))
##   waiting count
##1      78    15
##2      83    14
##3      81    13

head(agg(cube(df, "cyl", "disp", "gear"), avg(df$mpg)))
##  cyl  disp gear avg(mpg)
##1  NA 140.8    4     22.8
##2   4  75.7    4     30.4
##3   8 400.0    3     19.2
##4   8 318.0    3     15.5
##5  NA 351.0   NA     15.8
##6  NA 275.8   NA     16.3

head(agg(rollup(df, "cyl", "disp", "gear"), avg(df$mpg)))
##  cyl  disp gear avg(mpg)
##1   4  75.7    4     30.4
##2   8 400.0    3     19.2
##3   8 318.0    3     15.5
##4   4  78.7   NA     32.4
##5   8 304.0    3     15.2
##6   4  79.0   NA     27.3

# Convert waiting time from hours to seconds.
# Note that we can assign this to a new column in the same SparkDataFrame
df$waiting_secs <- df$waiting * 60
head(df)
##  eruptions waiting waiting_secs
##1     3.600      79         4740
##2     1.800      54         3240
##3     3.333      74         4440

# Convert waiting time from hours to seconds.
# Note that we can apply UDF to DataFrame.
schema <- structType(structField("eruptions", "double"), structField("waiting", "double"),
                     structField("waiting_secs", "double"))
df1 <- dapply(df, function(x) { x <- cbind(x, x$waiting * 60) }, schema)
head(collect(df1))
##  eruptions waiting waiting_secs
##1     3.600      79         4740
##2     1.800      54         3240
##3     3.333      74         4440
##4     2.283      62         3720
##5     4.533      85         5100
##6     2.883      55         3300

# Convert waiting time from hours to seconds.
# Note that we can apply UDF to DataFrame and return a R's data.frame
ldf <- dapplyCollect(
         df,
         function(x) {
           x <- cbind(x, "waiting_secs" = x$waiting * 60)
         })
head(ldf, 3)
##  eruptions waiting waiting_secs
##1     3.600      79         4740
##2     1.800      54         3240
##3     3.333      74         4440

# Determine six waiting times with the largest eruption time in minutes.
schema <- structType(structField("waiting", "double"), structField("max_eruption", "double"))
result <- gapply(
    df,
    "waiting",
    function(key, x) {
        y <- data.frame(key, max(x$eruptions))
    },
    schema)
head(collect(arrange(result, "max_eruption", decreasing = TRUE)))

##    waiting   max_eruption
##1      64       5.100
##2      69       5.067
##3      71       5.033
##4      87       5.000
##5      63       4.933
##6      89       4.900

# Determine six waiting times with the largest eruption time in minutes.
result <- gapplyCollect(
    df,
    "waiting",
    function(key, x) {
        y <- data.frame(key, max(x$eruptions))
        colnames(y) <- c("waiting", "max_eruption")
        y
    })
head(result[order(result$max_eruption, decreasing = TRUE), ])

##    waiting   max_eruption
##1      64       5.100
##2      69       5.067
##3      71       5.033
##4      87       5.000
##5      63       4.933
##6      89       4.900

# Perform distributed training of multiple models with spark.lapply. Here, we pass
# a read-only list of arguments which specifies family the generalized linear model should be.
families <- c("gaussian", "poisson")
train <- function(family) {
  model <- glm(Sepal.Length ~ Sepal.Width + Species, iris, family = family)
  summary(model)
}
# Return a list of model's summaries
model.summaries <- spark.lapply(families, train)

# Print the summary of each model
print(model.summaries)

# Start up spark session with eager execution enabled
sparkR.session(master = "local[*]",
               sparkConfig = list(spark.sql.repl.eagerEval.enabled = "true",
                                  spark.sql.repl.eagerEval.maxNumRows = as.integer(10)))

# Create a grouped and sorted SparkDataFrame
df <- createDataFrame(faithful)
df2 <- arrange(summarize(groupBy(df, df$waiting), count = n(df$waiting)), "waiting")

# Similar to R data.frame, displays the data returned, instead of SparkDataFrame class string
df2

##+-------+-----+
##|waiting|count|
##+-------+-----+
##|   43.0|    1|
##|   45.0|    3|
##|   46.0|    5|
##|   47.0|    4|
##|   48.0|    3|
##|   49.0|    5|
##|   50.0|    5|
##|   51.0|    6|
##|   52.0|    5|
##|   53.0|    7|
##+-------+-----+
##only showing top 10 rows

# Load a JSON file
people <- read.df("./examples/src/main/resources/people.json", "json")

# Register this SparkDataFrame as a temporary view.
createOrReplaceTempView(people, "people")

# SQL statements can be run by using the sql method
teenagers <- sql("SELECT name FROM people WHERE age >= 13 AND age <= 19")
head(teenagers)
##    name
##1 Justin

# Start up spark session with Arrow optimization enabled
sparkR.session(master = "local[*]",
               sparkConfig = list(spark.sql.execution.arrow.sparkr.enabled = "true"))

# Converts Spark DataFrame from an R DataFrame
spark_df <- createDataFrame(mtcars)

# Converts Spark DataFrame to an R DataFrame
collect(spark_df)

# Apply an R native function to each partition.
collect(dapply(spark_df, function(rdf) { data.frame(rdf$gear + 1) }, structType("gear double")))

# Apply an R native function to grouped data.
collect(gapply(spark_df,
               "gear",
               function(key, group) {
                 data.frame(gear = key[[1]], disp = mean(group$disp) > group$disp)
               },
               structType("gear double, disp boolean")))