If your rows may have NAs in them, I would process each column individually by first projecting the column ( map(x => x.nameOfColumn) ), filtering out the NAs, then running a summarizer over each column.
Even if you have many rows, after summarizing you will only have a vector of length #columns. On Mon, Jul 13, 2015 at 7:19 PM, Anupam Bagchi <anupam_bag...@rocketmail.com > wrote: > Hello Feynman, > > Actually in my case, the vectors I am summarizing over will not have the > same dimension since many devices will be inactive on some days. This is at > best a sparse matrix where we take only the active days and attempt to fit > a moving average over it. > > The reason I would like to save it to HDFS is that there are really > several million (almost a billion) devices for which this data needs to be > written. I am perhaps writing a very few columns, but the number of rows is > pretty large. > > Given the above two cases, is using MultivariateOnlineSummarizer not a > good idea then? > > Anupam Bagchi > > > On Jul 13, 2015, at 7:06 PM, Feynman Liang <fli...@databricks.com> wrote: > > Dimensions mismatch when adding new sample. Expecting 8 but got 14. > > Make sure all the vectors you are summarizing over have the same dimension. > > Why would you want to write a MultivariateOnlineSummary object (which can > be represented with a couple Double's) into a distributed filesystem like > HDFS? > > On Mon, Jul 13, 2015 at 6:54 PM, Anupam Bagchi < > anupam_bag...@rocketmail.com> wrote: > >> Thank you Feynman for the lead. >> >> I was able to modify the code using clues from the RegressionMetrics >> example. Here is what I got now. >> >> val deviceAggregateLogs = >> sc.textFile(logFile).map(DailyDeviceAggregates.parseLogLine).cache() >> >> // Calculate statistics based on bytes-transferred >> val deviceIdsMap = deviceAggregateLogs.groupBy(_.device_id) >> println(deviceIdsMap.collect().deep.mkString("\n")) >> >> val summary: MultivariateStatisticalSummary = { >> val summary: MultivariateStatisticalSummary = deviceIdsMap.map { >> case (deviceId, allaggregates) => Vectors.dense({ >> val sortedAggregates = allaggregates.toArray >> Sorting.quickSort(sortedAggregates) >> sortedAggregates.map(dda => dda.bytes.toDouble) >> }) >> }.aggregate(new MultivariateOnlineSummarizer())( >> (summary, v) => summary.add(v), // Not sure if this is really what I >> want, it just came from the example >> (sum1, sum2) => sum1.merge(sum2) // Same doubt here as well >> ) >> summary >> } >> >> It compiles fine. But I am now getting an exception as follows at Runtime. >> >> Exception in thread "main" org.apache.spark.SparkException: Job aborted >> due to stage failure: Task 1 in stage 3.0 failed 1 times, most recent >> failure: Lost task 1.0 in stage 3.0 (TID 5, localhost): >> java.lang.IllegalArgumentException: requirement failed: Dimensions mismatch >> when adding new sample. Expecting 8 but got 14. >> at scala.Predef$.require(Predef.scala:233) >> at >> org.apache.spark.mllib.stat.MultivariateOnlineSummarizer.add(MultivariateOnlineSummarizer.scala:70) >> at >> com.aeris.analytics.machinelearning.statistics.DailyDeviceStatisticsAnalyzer$$anonfun$4.apply(DailyDeviceStatisticsAnalyzer.scala:41) >> at >> com.aeris.analytics.machinelearning.statistics.DailyDeviceStatisticsAnalyzer$$anonfun$4.apply(DailyDeviceStatisticsAnalyzer.scala:41) >> at >> scala.collection.TraversableOnce$$anonfun$foldLeft$1.apply(TraversableOnce.scala:144) >> at >> scala.collection.TraversableOnce$$anonfun$foldLeft$1.apply(TraversableOnce.scala:144) >> at scala.collection.Iterator$class.foreach(Iterator.scala:727) >> at scala.collection.AbstractIterator.foreach(Iterator.scala:1157) >> at >> scala.collection.TraversableOnce$class.foldLeft(TraversableOnce.scala:144) >> at scala.collection.AbstractIterator.foldLeft(Iterator.scala:1157) >> at >> scala.collection.TraversableOnce$class.aggregate(TraversableOnce.scala:201) >> at >> scala.collection.AbstractIterator.aggregate(Iterator.scala:1157) >> at org.apache.spark.rdd.RDD$$anonfun$26.apply(RDD.scala:966) >> at org.apache.spark.rdd.RDD$$anonfun$26.apply(RDD.scala:966) >> at >> org.apache.spark.SparkContext$$anonfun$32.apply(SparkContext.scala:1533) >> at >> org.apache.spark.SparkContext$$anonfun$32.apply(SparkContext.scala:1533) >> at >> org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:61) >> at org.apache.spark.scheduler.Task.run(Task.scala:64) >> at >> org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:203) >> at >> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) >> at >> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) >> at java.lang.Thread.run(Thread.java:722) >> >> Can’t tell where exactly I went wrong. Also, how do I take the >> MultivariateOnlineSummary object and write it to HDFS? I have the >> MultivariateOnlineSummary object with me, but I really need an RDD to call >> saveAsTextFile() on it. >> >> Anupam Bagchi >> >> >> On Jul 13, 2015, at 4:52 PM, Feynman Liang <fli...@databricks.com> wrote: >> >> A good example is RegressionMetrics >> <https://github.com/apache/spark/blob/master/mllib/src/main/scala/org/apache/spark/mllib/evaluation/RegressionMetrics.scala#L48>'s >> use of of OnlineMultivariateSummarizer to aggregate statistics across >> labels and residuals; take a look at how aggregateByKey is used there. >> >> On Mon, Jul 13, 2015 at 4:50 PM, Anupam Bagchi < >> anupam_bag...@rocketmail.com> wrote: >> >>> Thank you Feynman for your response. Since I am very new to Scala I may >>> need a bit more hand-holding at this stage. >>> >>> I have been able to incorporate your suggestion about sorting - and it >>> now works perfectly. Thanks again for that. >>> >>> I tried to use your suggestion of using MultiVariateOnlineSummarizer, >>> but could not proceed further. For each deviceid (the key) my goal is to >>> get a vector of doubles on which I can query the mean and standard >>> deviation. Now because RDDs are immutable, I cannot use a foreach loop to >>> interate through the groupby results and individually add the values in an >>> RDD - Spark does not allow that. I need to apply the RDD functions directly >>> on the entire set to achieve the transformations I need. This is where I am >>> faltering since I am not used to the lambda expressions that Scala uses. >>> >>> object DeviceAnalyzer { >>> def main(args: Array[String]) { >>> val sparkConf = new SparkConf().setAppName("Device Analyzer") >>> val sc = new SparkContext(sparkConf) >>> >>> val logFile = args(0) >>> >>> val deviceAggregateLogs = >>> sc.textFile(logFile).map(DailyDeviceAggregates.parseLogLine).cache() >>> >>> // Calculate statistics based on bytes >>> val deviceIdsMap = deviceAggregateLogs.groupBy(_.device_id) >>> >>> // Question: Can we not write the line above as >>> deviceAggregateLogs.groupBy(_.device_id).sortBy(c => c_.2, true) // >>> Anything wrong? >>> >>> // All I need to do below is collect the vector of bytes for each >>> device and store it in the RDD >>> >>> // The problem with the ‘foreach' approach below, is that it generates >>> the vector values one at a time, which I cannot >>> >>> // add individually to an immutable RDD >>> >>> deviceIdsMap.foreach(a => { >>> val device_id = a._1 // This is the device ID >>> val allaggregates = a._2 // This is an array of all >>> device-aggregates for this device >>> >>> val sortedaggregates = allaggregates.toArray >>> Sorting.quickSort(sortedaggregates) >>> >>> val byteValues = sortedaggregates.map(dda => >>> dda.bytes.toDouble).toArray >>> val count = byteValues.count(A => true) >>> val sum = byteValues.sum >>> val xbar = sum / count >>> val sum_x_minus_x_bar_square = byteValues.map(x => >>> (x-xbar)*(x-xbar)).sum >>> val stddev = math.sqrt(sum_x_minus_x_bar_square / count) >>> >>> val vector: Vector = Vectors.dense(byteValues) >>> println(vector) >>> println(device_id + "," + xbar + "," + stddev) >>> }) >>> >>> //val vector: Vector = Vectors.dense(byteValues) >>> //println(vector) >>> //val summary: MultivariateStatisticalSummary = >>> Statistics.colStats(vector) >>> >>> >>> sc.stop() } } >>> >>> Can you show me how to write the ‘foreach’ loop in a Spark-friendly way? >>> Thanks a lot for your help. >>> >>> Anupam Bagchi >>> >>> >>> On Jul 13, 2015, at 12:21 PM, Feynman Liang <fli...@databricks.com> >>> wrote: >>> >>> The call to Sorting.quicksort is not working. Perhaps I am calling it >>>> the wrong way. >>> >>> allaggregates.toArray allocates and creates a new array separate from >>> allaggregates which is sorted by Sorting.quickSort; allaggregates. Try: >>> val sortedAggregates = allaggregates.toArray >>> Sorting.quickSort(sortedAggregates) >>> >>>> I would like to use the Spark mllib class >>>> MultivariateStatisticalSummary to calculate the statistical values. >>> >>> MultivariateStatisticalSummary is a trait (similar to a Java interface); >>> you probably want to use MultivariateOnlineSummarizer. >>> >>>> For that I would need to keep all my intermediate values as RDD so that >>>> I can directly use the RDD methods to do the job. >>> >>> Correct; you would do an aggregate using the add and merge functions >>> provided by MultivariateOnlineSummarizer >>> >>>> At the end I also need to write the results to HDFS for which there is >>>> a method provided on the RDD class to do so, which is another reason I >>>> would like to retain everything as RDD. >>> >>> You can write the RDD[(device_id, MultivariateOnlineSummarizer)] to >>> HDFS, or you could unpack the relevant statistics from >>> MultivariateOnlineSummarizer into an array/tuple using a mapValues first >>> and then write. >>> >>> On Mon, Jul 13, 2015 at 10:07 AM, Anupam Bagchi < >>> anupam_bag...@rocketmail.com> wrote: >>> >>>> I have to do the following tasks on a dataset using Apache Spark with >>>> Scala as the programming language: >>>> >>>> 1. Read the dataset from HDFS. A few sample lines look like this: >>>> >>>> >>>> deviceid,bytes,eventdate15590657,246620,2015063014066921,1907,2015062114066921,1906,201506266522013,2349,201506266522013,2525,20150613 >>>> >>>> >>>> 1. Group the data by device id. Thus we now have a map of deviceid >>>> => (bytes,eventdate) >>>> 2. For each device, sort the set by eventdate. We now have an >>>> ordered set of bytes based on eventdate for each device. >>>> 3. Pick the last 30 days of bytes from this ordered set. >>>> 4. Find the moving average of bytes for the last date using a time >>>> period of 30. >>>> 5. Find the standard deviation of the bytes for the final date >>>> using a time period of 30. >>>> 6. Return two values in the result (mean - k*stddev) and (mean + >>>> k*stddev) >>>> [Assume k = 3] >>>> >>>> I am using Apache Spark 1.3.0. The actual dataset is wider, and it has >>>> to run on a billion rows finally. >>>> Here is the data structure for the dataset. >>>> >>>> package com.testingcase class DeviceAggregates ( >>>> device_id: Integer, >>>> bytes: Long, >>>> eventdate: Integer >>>> ) extends Ordered[DailyDeviceAggregates] { >>>> def compare(that: DailyDeviceAggregates): Int = { >>>> eventdate - that.eventdate >>>> }}object DeviceAggregates { >>>> def parseLogLine(logline: String): DailyDeviceAggregates = { >>>> val c = logline.split(",") >>>> DailyDeviceAggregates(c(0).toInt, c(1).toLong, c(2).toInt) >>>> }} >>>> >>>> The DeviceAnalyzer class looks like this: >>>> I have a very crude implementation that does the job, but it is not up >>>> to the mark. Sorry, I am very new to Scala/Spark, so my questions are quite >>>> basic. Here is what I have now: >>>> >>>> import com.testing.DailyDeviceAggregatesimport >>>> org.apache.spark.{SparkContext, SparkConf}import >>>> org.apache.spark.mllib.linalg.Vectorimport >>>> org.apache.spark.mllib.stat.{MultivariateStatisticalSummary, >>>> Statistics}import org.apache.spark.mllib.linalg.{Vector, Vectors} >>>> import scala.util.Sorting >>>> object DeviceAnalyzer { >>>> def main(args: Array[String]) { >>>> val sparkConf = new SparkConf().setAppName("Device Analyzer") >>>> val sc = new SparkContext(sparkConf) >>>> >>>> val logFile = args(0) >>>> >>>> val deviceAggregateLogs = >>>> sc.textFile(logFile).map(DailyDeviceAggregates.parseLogLine).cache() >>>> >>>> // Calculate statistics based on bytes >>>> val deviceIdsMap = deviceAggregateLogs.groupBy(_.device_id) >>>> >>>> deviceIdsMap.foreach(a => { >>>> val device_id = a._1 // This is the device ID >>>> val allaggregates = a._2 // This is an array of all >>>> device-aggregates for this device >>>> >>>> println(allaggregates) >>>> Sorting.quickSort(allaggregates.toArray) // Sort the CompactBuffer >>>> of DailyDeviceAggregates based on eventdate >>>> println(allaggregates) // This does not work - results are not >>>> sorted !! >>>> >>>> val byteValues = allaggregates.map(dda => dda.bytes.toDouble).toArray >>>> val count = byteValues.count(A => true) >>>> val sum = byteValues.sum >>>> val xbar = sum / count >>>> val sum_x_minus_x_bar_square = byteValues.map(x => >>>> (x-xbar)*(x-xbar)).sum >>>> val stddev = math.sqrt(sum_x_minus_x_bar_square / count) >>>> >>>> val vector: Vector = Vectors.dense(byteValues) >>>> println(vector) >>>> println(device_id + "," + xbar + "," + stddev) >>>> >>>> //val vector: Vector = Vectors.dense(byteValues) >>>> //println(vector) >>>> //val summary: MultivariateStatisticalSummary = >>>> Statistics.colStats(vector) >>>> }) >>>> >>>> sc.stop() >>>> }} >>>> >>>> I would really appreciate if someone can suggests improvements for the >>>> following: >>>> >>>> 1. The call to Sorting.quicksort is not working. Perhaps I am >>>> calling it the wrong way. >>>> 2. I would like to use the Spark mllib class >>>> MultivariateStatisticalSummary to calculate the statistical values. >>>> 3. For that I would need to keep all my intermediate values as RDD >>>> so that I can directly use the RDD methods to do the job. >>>> 4. At the end I also need to write the results to HDFS for which >>>> there is a method provided on the RDD class to do so, which is another >>>> reason I would like to retain everything as RDD. >>>> >>>> >>>> Thanks in advance for your help. >>>> >>>> Anupam Bagchi >>>> >>>> >>> >>> >>> >> >> > >