Splitting string in dataset Apache Spark - scala
I am absolutely new in Spark
I have a txt dataset with cathegorical attributes, looking like this:
10000,5,0,1,0,0,5,3,2,2,1,0,1,0,4,3,0,2,0,0,1,0,0,0,0,10,0,1,0,1,0,1,4,2,2,3,0,2,0,2,1,4,3,0,0,0,3,1,0,3,22,0,3,0,1,0,1,0,0,0,5,0,2,1,1,0,11,1,0
10001,6,1,1,0,0,7,5,2,2,0,0,3,0,1,1,0,1,0,0,0,0,1,0,0,4,0,2,0,0,0,1,4,1,2,2,0,2,0,2,2,4,2,1,0,0,1,1,0,2,10,0,1,0,1,0,1,0,0,0,1,0,2,1,1,0,5,1,0
10002,3,1,2,0,0,7,4,2,2,0,0,1,0,4,4,0,1,0,1,0,0,0,0,0,1,0,2,0,4,0,10,4,1,2,4,0,2,0,2,1,4,2,2,0,0,0,1,0,2,10,0,6,0,1,0,1,0,0,0,2,0,2,1,1,0,10,1,0
10003,4,1,2,0,0,1,3,2,2,0,0,3,0,3,3,0,1,0,0,0,0,0,0,1,4,0,2,0,2,0,1,4,1,2,2,0,2,0,2,1,2,2,0,0,0,1,1,0,2,10,0,4,0,1,0,1,0,0,0,1,0,1,1,1,0,10,1,0
10004,7,1,1,0,0,0,0,2,2,0,0,3,0,0,0,0,0,0,0,0,1,0,0,0,0,0,2,2,0,0,0,4,1,2,0,0,2,0,2,1,4,0,1,0,0,0,6,0,2,22,0,1,0,1,0,1,0,0,3,0,0,0,2,2,0,5,6,0
10005,1,1,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,0,4,0,0,0,1,0,0,0,0,0,2,0,4,0,2,0,121,0,0,1,0,10,1,0,0,2,0,1,0,0,0,0,0,0,0,0,0,4,0,0
10006,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,0,4,0,0,0,1,0,0,0,0,0,2,1,0,0,2,0,121,0,0,1,0,10,1,0,0,2,0,0,0,0,0,0,0,0,0,0,0,4,0,0
10007,4,1,2,0,0,6,0,2,2,0,0,4,0,5,5,0,2,1,0,0,0,0,0,0,9,0,2,0,0,0,11,4,1,2,3,0,2,0,2,1,2,3,1,0,0,0,1,0,3,10,0,1,0,1,0,1,0,0,0,0,0,2,1,1,0,11,1,0
10008,6,1,1,0,0,1,0,2,2,0,0,7,0,1,0,0,1,0,0,0,0,0,0,0,7,0,2,2,0,0,0,4,1,2,6,0,2,0,2,1,2,2,1,0,0,0,6,0,2,10,0,1,0,1,0,1,0,0,3,0,0,1,1,2,0,10,1,0
10009,3,1,12,0,0,1,0,2,2,0,0,0,0,3,0,0,1,0,0,0,0,0,0,0,4,0,2,2,4,0,0,2,1,2,6,0,2,0,2,1,0,2,2,0,0,0,3,0,2,10,0,6,1,1,1,0,0,0,1,0,0,1,1,2,0,8,1,1
10010,5,11,1,0,0,1,3,2,2,0,0,0,0,3,3,0,3,0,0,0,0,0,0,0,6,0,2,0,0,0,1,4,1,2,1,0,2,0,2,1,0,4,0,0,0,1,1,0,4,21,0,1,0,1,0,0,0,0,0,4,0,2,1,1,0,11,1,0
10011,4,0,1,0,0,1,5,2,2,0,0,3,0,1,1,0,1,0,0,0,0,0,0,0,7,0,2,0,0,0,1,4,1,2,1,0,2,0,2,1,3,2,1,0,0,1,1,0,2,10,0,1,0,1,0,1,0,0,0,2,0,2,1,1,0,10,1,0
10012,1,1,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,4,0,0,0,0,0,0,0,0,0,2,0,0,0,2,0,112,0,0,1,0,10,1,0,0,1,0,0,0,0,0,0,0,0,0,2,0,1,0,0
10013,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,0,4,0,0,0,1,0,0,0,0,0,2,1,4,0,2,0,121,0,0,1,0,10,1,0,0,2,0,1,0,0,0,0,0,0,0,0,0,4,0,0
10014,3,11,1,0,0,6,4,2,2,0,0,1,0,2,2,0,0,1,0,0,0,0,0,0,3,0,2,0,3,0,1,4,2,2,5,0,2,0,1,2,4,2,10,0,0,1,1,0,2,10,0,5,0,1,0,1,0,0,0,3,0,1,1,1,0,7,1,0
10015,4,3,1,0,0,1,3,2,2,1,0,0,0,3,5,0,3,0,0,1,0,0,0,0,4,0,1,0,0,1,1,2,2,2,2,0,2,0,2,0,0,4,0,0,0,1,1,0,4,10,0,1,3,1,1,0,0,0,0,3,0,2,1,1,0,11,1,1
10016,4,11,1,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,2,2,4,0,0,4,1,1,0,0,1,0,0,2,0,0,12,0,0,0,6,0,2,23,0,6,0,1,0,0,0,0,3,0,0,0,2,0,0,5,7,0
10017,7,1,1,0,0,0,0,2,2,0,0,3,0,0,0,0,0,0,0,1,1,0,1,0,0,0,2,2,0,0,0,4,1,2,0,0,2,0,2,1,4,0,1,0,0,0,6,0,2,10,0,1,0,1,0,1,0,0,3,0,0,0,2,2,0,6,6,0
The task is to get the number of strings, where numeral on 57th position
10001,6,1,1,0,0,7,5,2,2,0,0,3,0,1,1,0,1,0,0,0,0,1,0,0,4,0,2,0,0,0,1,4,1,2,2,0,2,0,2,2,4,2,1,0,0,1,1,0,2,10,0,1,0,1,0,((1)),0,0,0,1,0,2,1,1,0,5,1,0
is 1 . The problem is that strings are the elements of the RDD, so I need to split each string and make an array(x,y) to get the position i need.
I tried to use
val censusText = sc.textFile("USCensus1990.data.txt")
val splitRDD = censusText.map(line=>line.split(","))
but It didn't help
But I have no idea how to do it.
Can you please help me
You can try:
censusText.filter(l => l.split(",")(56) == "1").count
// res5: Long = 12
Or you can first split the RDD then do the filter / count:
val splitRDD = censusText.map(l => l.split(","))
splitRDD.filter(r => r(56) == "1").count
// res7: Long = 12
Related
replace multiple occurrence of duplicate string in Scala with empty
I have a string as something,'' something,nothing_something,op nothing_something,'' cat,cat I want to achieve my output as '' something,op nothing_something,cat Is there any way to achieve it?
If I understand your requirement correctly, here's one approach with the following steps:
Split the input string by "," and create a list of indexed-CSVs and convert it to a Map
Generate 2-combinations of the indexed-CSVs
Check each of the indexed-CSV pairs and capture the index of any CSV which is contained within the other CSV
Since the CSVs corresponding to the captured indexes are contained within some other CSV, removing these indexes will result in remaining indexes we would like to keep
Use the remaining indexes to look up CSVs from the CSV Map and concatenate them back to a string
Here is sample code applying to a string with slightly more general comma-separated values:
val str = "cats,a cat,cat,there is a cat,my cat,cats,cat"
val csvIdxList = (Stream from 1).zip(str.split(",")).toList
val csvMap = csvIdxList.toMap
val csvPairs = csvIdxList.combinations(2).toList
val csvContainedIdx = csvPairs.collect{
case List(x, y) if x._2.contains(y._2) => y._1
case List(x, y) if y._2.contains(x._2) => x._1
}.
distinct
// csvContainedIdx: List[Int] = List(3, 6, 7, 2)
val csvToKeepIdx = (1 to csvIdxList.size) diff csvContainedIdx
// csvToKeepIdx: scala.collection.immutable.IndexedSeq[Int] = Vector(1, 4, 5)
val strDeduped = csvToKeepIdx.map( csvMap.getOrElse(_, "") ).mkString(",")
// strDeduped: String = cats,there is a cat,my cat
Applying the above to your sample string something,'' something,nothing_something,op nothing_something would yield the expected result:
strDeduped: String = '' something,op nothing_something
First create an Array of words separated by commas using split command on the given String, and do other operations using filter and mkString as below:
s.split(",").filter(_.contains(' ')).mkString(",")
In Scala REPL:
scala> val s = "something,'' something,nothing_something,op nothing_something"
s: String = something,'' something,nothing_something,op nothing_something
scala> s.split(",").filter(_.contains(' ')).mkString(",")
res27: String = '' something,op nothing_something
As per Leo C comment, I tested it as below with some other String:
scala> val s = "something,'' something anything anything anything anything,nothing_something,op op op nothing_something"
s: String = something,'' something anything anything anything anything,nothing_something,op op op nothing_something
scala> s.split(",").filter(_.contains(' ')).mkString(",")
res43: String = '' something anything anything anything anything,op op op nothing_something
Finding length of string in Scala
I am a newbie to scala I have a list of strings - List[String] (“alpha”, “gamma”, “omega”, “zeta”, “beta”) I want to count all the strings with length = 4 i.e I want to get output = 2.
You can do like this:
val data = List("alpha", "gamma", "omega", "zeta", "beta")
data.filter(x => x.length == 4).size
res8: Int = 2
You can just use count function as
val list = List[String] ("alpha", "gamma", "omega", "zeta", "beta")
println(list.count(x => x.length == 4))
//2 is printed
I hope the answer is helpful
Is there a better way of converting Iterator[char] to Seq[String]?
Following is my code that I have used to convert Iterator[char] to Seq[String].
val result = IOUtils.toByteArray(new FileInputStream (new File(fileDir)))
val remove_comp = result.grouped(11).map{arr => arr.update(2, 32);arr}.flatMap{arr => arr.update(3, 32); arr}
val convert_iter = remove_comp.map(_.toChar.toString).toSeq.mkString.split("\n")
val rdd_input = Spark.sparkSession.sparkContext.parallelize(convert_iter)
val fileDir:
12**34567890
12##34567890
12!!34567890
12¬¬34567890
12
'34567890
I am not happy with this code as the data size is big and converting to string would end up with heap space.
val convert_iter = remove_comp.map(_.toChar)
convert_iter: Iterator[Char] = non-empty iterator
Is there a better way of coding?
By completely disregarding corner cases about empty Strings etc I would start with something like:
val test = Iterable('s','f','\n','s','d','\n','s','v','y')
val (allButOne, last) = test.foldLeft( (Seq.empty[String], Seq.empty[Char]) ) {
case ((strings, chars), char) =>
if (char == '\n')
(strings :+ chars.mkString, Seq.empty)
else
(strings, chars :+ char)
}
val result = allButOne :+ last.mkString
I am sure it could be made more elegant, and handle corner cases better (once you define you want them handled), but I think it is a nice starting point.
But to be honest I am not entirely sure what you want to achieve. I just guessed that you want to group chars divided by \n together and turn them into Strings.
Looking at your code, I see that you are trying to replace the special characters such as **, ## and so on from the file that contains following data
12**34567890
12##34567890
12!!34567890
12¬¬34567890
12
'34567890
For that you can just read the data using sparkContext textFile and use regex replaceAllIn
val pattern = new Regex("[¬~!##$^%&*\\(\\)_+={}\\[\\]|;:\"'<,>.?` /\\-]")
val result = sc.textFile(fileDir).map(line => pattern.replaceAllIn(line, ""))
and you should have you result as RDD[String] which also an iterator
1234567890
1234567890
1234567890
1234567890
12
34567890
Updated
If there are \n and \r in between the texts at 3rd and 4th place and if the result is all fixed length of 10 digits text then you can use wholeTextFiles api of sparkContext and use following regex as
val pattern = new Regex("[¬~!##$^%&*\\(\\)_+={}\\[\\]|;:\"'<,>.?` /\\-\r\n]")
val result = sc.wholeTextFiles(fileDir).flatMap(line => pattern.replaceAllIn(line._2, "").grouped(10))
You should get the output as
1234567890
1234567890
1234567890
1234567890
1234567890
I hope the answer is helpful
How to select several element from an RDD file line using Spark in Scala
I'm new in spark and scala and I would like to select several columns from a dataset.
I transformed my data in RDD a file using :
val dataset = sc.textFile(args(0))
Then I split my line
val resu = dataset.map(line => line.split("\001"))
But I in my dataset I have a lot of features and I just want to keep some of then (colums 2 and 3)
I tried this (which works with Pyspark) but It does'nt work.
val resu = dataset.map(line => line.split("\001")[2,3])
I know this is a newbie question but is there someone who can help me ? thanks.
I just want to keep some of then (colums 2 and 3)
If you want columns 2 and 3 in tuple form you can do
val resu = dataset.map(line => {
val array = line.split("\001")
(array(2), array(3))
})
But if you want column 2 and 3 in array form then you can do
val resu = dataset.map(line => {
val array = line.split("\001")
Array(array(2), array(3))
})
In Scala, in order to access to specific list elements you have to use parentheses.
In your case, you want a sublist, so you can try the slice(i, j) function. It extracts the elements from the index i to the j-1. So in your case, you may use:
val resu = dataset.map(line => line.split("\001").slice(2,4))
Hope it helps.
Spark scala filter multiple rdd based on string length
I am trying to solve one of the quiz, the question is as below,
Write the missing code in the given program to display the expected output to identify animals that have names with four
letters.
Output: Array((4,lion))
Program
val a = sc.parallelize(List("dog","tiger","lion","cat","spider","eagle"),2)
val b = a.keyBy(_.length)
val c = sc.parallelize(List("ant","falcon","squid"),2)
val d = c.keyBy(_.length)
I have tried to write code in spark shell but get stuck with syntax to add 4 RDD and applying filter.
How about using the PairRDD lookup method: b.lookup(4).toArray // res1: Array[String] = Array(lion) d.lookup(4).toArray // res2: Array[String] = Array()