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Java String split not returning the right values
(4 answers)
Closed 10 months ago.
I am trying to create a spark dataframe from text file in which data is delimited by | symbol.
Have to Spark with Scala.
The text files has data as below:
John|1234|$2500|giggle
Ross|1344|$5500|Micsoft
Jennifer|5432|$2100|healthcare
val schemaString = "name,employeeid,salary,company"
val fields = schemaString.split(",").map(fieldName => StructField(fieldName,StringType, nullable=true))
val schema = StructType(fields)
val rddView= sc.textFile("/dev/path/*").map(_.split("|")).map{x
=> org.apache.spark.sql.Row(x:_*)}
val rddViewDf = sqlContext.createDataFrame(rddView,schema)
rddViewDf.show()
Expecting the values to be mapped to corresponding columns but output is not as expected.
Can someone provide the correct solution in Spark using scala language
Output I am getting:
+----+----------+------+-------+
|name|employeeid|salary|company|
+----+----------+------+-------+
| J| o| h| n|
| R| o| s| s|
| J| e| n| n|
+----+----------+------+-------+
Expected Output
+----------+------------+----------+-----------+
|name |employeeid | salary| company|
+---------+-------------+----------+-----------+
| John| 1234| $2500| giggle|
| Ross| 1344| $5500| Micsoft|
| Jennifer| 5432| $2100| healthcare|
+----+----------+------+-----------------------+
As pointed out in the comments, your split delimeter is incorrect.
However, you should not be using RDDs anyway
scala> spark.read.option("delimiter", "|").csv("data.txt").show()
+--------+----+-----+----------+
| _c0| _c1| _c2| _c3|
+--------+----+-----+----------+
| John|1234|$2500| giggle|
| Ross|1344|$5500| Micsoft|
|Jennifer|5432|$2100|healthcare|
+--------+----+-----+----------+
https://spark.apache.org/docs/latest/sql-data-sources-csv.html
To rename the columns, please see this and translate to Scala How to read csv without header and name them with names while reading in pyspark?
Note: Ideally, your employeeId column is defined as a LongType, not StringType
Related
I am trying to add an Array of values as a new column to the DataFrame.
Ex:
Lets assume there is an Array(4,5,10) and a dataframe
+----------+-----+
| name | age |
+----------+-----+
| John | 32 |
| Elizabeth| 28 |
| Eric | 41 |
+----------+-----+
My requirement is to add the above array as a new column to the dataframe. My expected output is as follows:
+----------+-----+------+
| name | age | rank |
+----------+-----+------+
| John | 32 | 4 |
| Elizabeth| 28 | 5 |
| Eric | 41 | 10 |
+----------+-----+------+
I am trying if I can achieve this using rdd and zipWithIndex.
df.rdd.zipWithIndex.map(_.swap).join(array_rdd.zipWithIndex.map(_.swap))
This is resulting in something of this sort.
(0,([John, 32],4))
I want to convert the above RDD back to required dataframe. Let me know how to achieve this.
Are there any alternatives available for achieving the desired result other than using rdd and zipWithIndex? What is the best way to do it?
PS:
Context for better understanding:
I am using Xpress optimization suite to solve a mathematical problem. Xpress takes inputs interms of Arrays and also outputs the result in an Array. I get input as a DataFrame and I am extracting columns as Arrays(using collect) and passing to Xpress. Xpress outputs Array[Double] as solution. I want to add this solution back to the dataframe as a column and every value in the solution array corresponds to the row of the dataframe at its index i.e value at index 'n' of the output Array corresponds to 'n'th row of the dataframe
After the join just map the results to what you are looking for.
You can convert this back to a dataframe after joining the RDDs.
val originalDF = Seq(("John", 32), ("Elizabeth", 28), ("Eric", 41)).toDF("name", "age")
val rank = Array(4, 5, 10)
// convert to Seq first
val rankDF = rank.toSeq.toDF("rank")
val joined = originalDF.rdd.zipWithIndex.map(_.swap).join(rankDF.rdd.zipWithIndex.map(_.swap))
val finalRDD = joined.map{ case (k,v) => (k, v._1.getString(0), v._1.getInt(1), v._2.getInt(0)) }
val finalDF = finalRDD.toDF("id", "name", "age", "rank")
finalDF.show()
/*
+---+---------+---+----+
| id| name|age|rank|
+---+---------+---+----+
| 0| John| 32| 4|
| 1|Elizabeth| 28| 5|
| 2| Eric| 41| 10|
+---+---------+---+----+
*/
The only alternate way that I can think of is to use the org.apache.spark.sql.functions.row_number() window function. This essentially achieves the same thing by adding an increasing, consecutive row number to the dataframe.
The drawback with this is the large amount of data shuffle into one partition, since we need to have unrepeated row numbers for all rows in the dataframe. If your data is very large this can lead to an out of memory issue. (Note: this may not be applicable in your case, since you mentioned you are doing a collect on the data and have not mentioned any memory issues in this).
The approach of converting to an rdd and using zipWithIndex is an acceptable solution, but generally converting from dataframe to rdd is not recommended due to the performance difference of using an RDD instead of a dataframe.
I'm trying to calculate a fuzzy score (preferable partial_ratio score) across two columns in the same dataframe.
| column1 | column2|
| -------- | -------------- |
| emmett holt| holt
| greenwald| christopher
It would need to look something like this:
| column1 | column2|partial_ratio|
| -------- | -------------- |-----------|
| emmett holt| holt|100|
| greenwald| christopher|22|
|schaefer|schaefer|100|
With the help of another question on this website, I worked towards the following code:
compare=pd.MultiIndex.from_product([ dataframe['column1'],dataframe ['column2'] ]).to_series()
def metrics (tup):
return pd.Series([fuzz.partial_ratio(*tup)], ['partial_ratio'])
df['partial_ratio'] = df.apply(lambda x: fuzz.partial_ratio(x['original_title'], x['title']), axis=1)
But the problem already starts with the first line of the code that returns the following error notification:
Cannot convert column into bool: please use '&' for 'and', '|' for 'or', '~' for 'not' when building DataFrame boolean expressions.
You can say I'm kind of stuck here so any advice on this is appreciated!
You need a UDF to use fuzzywuzzy:
from fuzzywuzzy import fuzz
import pyspark.sql.functions as F
#F.udf
def fuzzyudf(original_title, title):
return fuzz.partial_ratio(original_title, title)
df2 = df.withColumn('partial_ratio', fuzzyudf('column1', 'column2'))
df2.show()
+-----------+-----------+-------------+
| column1| column2|partial_ratio|
+-----------+-----------+-------------+
|emmett holt| holt| 100|
| greenwald|christopher| 22|
+-----------+-----------+-------------+
So I have a table (sample)
I'm using pyspark dataframe APIs to filter out the 'NOC's that has never won a gold medal and here's the code I write
First part of my code
from pyspark.sql import SQLContext
from pyspark.sql.types import *
from pyspark.sql.functions import *
spark = SQLContext(sc)
df1 = spark.read.format("csv").options(header = 'true').load("D:\\datasets\\athlete_events.csv")
df = df1.na.replace('NA', '-')
countgdf = gdf.groupBy('NOC').agg(count('Medal').alias('No of Gold medals')).select('NOC').show()
It will generate the output
+---+
|NOC|
+---+
|POL|
|JAM|
|BRA|
|ARM|
|MOZ|
|JOR|
|CUB|
|FRA|
|ALG|
|BRN|
+---+
only showing top 10 rows
The next part of the code is something like
allgdf = df.select('NOC').distinct()
This display the output
+-----------+
| NOC|
+-----------+
| DeRuyter|
| POL|
| Russia|
| JAM|
| BUR|
| BRA|
| ARM|
| MOZ|
| CUB|
| JOR|
| Sweden|
| FRA|
| ALG|
| SOM|
| IVB|
|Philippines|
| BRN|
| MAL|
| COD|
| FSM|
+-----------+
Notice the values that are more than 3 characters? Those are supposed to be the values of the column 'Team' but I'm not sure why those values are getting displayed in 'NOC' column. It's hard to figure out why this is happening i.e illegal values in the column.
When I write the final code
final = allgdf.subtract(countgdf).show()
The same happens as illegal values appear in the final dataframe column.
Any help would be appericiated. Thanks.
You should specify a delimiter for your CSV file. By default Spark is using comma separators (,)
This can be done, for example, with :
.option("delimiter",";")
I have a column col1 that represents a GPS coordinate format:
25 4.1866N 55 8.3824E
I would like to split it in multiple columns based on white-space as separator, as in the output example table_example below:
| 1st_split | 2nd_split | 3rd_split | 4th_split |
|:-----------|------------:|:------------:|:------------:|
| 25 | 4.1866N | 55 | 8.3824E |
Considering the fact that there is the split() function, I have tried in this way:
SELECT explode(split(`col1`, ' ')) AS `col` FROM table_example;
But, instead of splitting per multiple columns, it splits per multiple rows, like in the output below:
Can someone clarify me which would be the worth approach for get the expected result?
If you have a dataframe as
+---------------------+
|col |
+---------------------+
|25 4.1866N 55 8.3824E|
+---------------------+
Using Scala API
You can simply use split inbuilt function and select appropriately as
import org.apache.spark.sql.functions._
df.withColumn("split", split(col("col"), " "))
.select(col("split")(0).as("1st_split"), col("split")(1).as("2nd_split"),col("split")(2).as("3rd_split"),col("split")(3).as("4th_split"))
.show(false)
which would give you
+---------+---------+---------+---------+
|1st_split|2nd_split|3rd_split|4th_split|
+---------+---------+---------+---------+
|25 |4.1866N |55 |8.3824E |
+---------+---------+---------+---------+
Using SQL way
Sql is much easier and similar to the api way
df.createOrReplaceTempView("table_example")
val splitted = sqlContext.sql("SELECT split(`col`, ' ') AS `col` FROM table_example")
splitted.createOrReplaceTempView("splitted_table")
val result = sqlContext.sql("SELECT `col`[0] AS `1st_split`, `col`[1] AS `2nd_split`, `col`[2] AS `3rd_split`, `col`[3] AS `4th_split` FROM splitted_table")
result.show(false)
I hope the answer is helpful
How can we merge 2 dataframes and form a new data using conditions.for eg.
if data is present in dataframe B , use the row from dataframe B else use data from dataframe A.
DataFrame A
+-----+-------------------+--------+------+
| Name| LastTime|Duration|Status|
+-----+-------------------+--------+------+
| Bob|2015-04-23 12:33:00| 1|logout|
|Alice|2015-04-20 12:33:00| 5| login|
+-----+-------------------+--------+------+
DataFrame B
+-----+-------------------+--------+------+
| Name| LastTime|Duration|Status|
+-----+-------------------+--------+------+
| Bob|2015-04-24 00:33:00| 1|login |
+-----+-------------------+--------+------+
I want to form a new dataframe by using whole data in Dataframe A but update rows using data in B
+-----+-------------------+--------+------+
| Name| LastTime|Duration|Status|
+-----+-------------------+--------+------+
| Bob|2015-04-24 00:33:00| 1|login |
|Alice|2015-04-20 12:33:00| 5| login|
+-----+-------------------+--------+------+
I tried full outer join as
val joined = df.as("a").join(df.as("b")).where($"a.name" === $"b.name","outer")
But it resulted in 1 row with duplicate columns.How can I ignore the row in first table if there is one corresponding row is present in second.
val combined_df = dfa.join(dfb,Seq("Name"),"right").select(dfa("Name"), coalesce(dfa("LastTime"), dfb("LastTime")), coalesce(dfa("Duration"), dfb("Duration")),coalesce(dfa("Status"), dfb("Status")))