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From Umesh Kacha <umesh.ka...@gmail.com>
Subject Re: How to calculate percentile of a column of DataFrame?
Date Mon, 12 Oct 2015 18:52:01 GMT
Hi Ted thanks much for the detailed answer and appreciate your efforts. Do
we need to register Hive UDFs?

sqlContext.udf.register("percentile_approx");???//is it valid?

I am calling Hive UDF percentile_approx in the following manner which gives
compilation error

df.select("col1").groupby("col1").agg(callUdf("percentile_approx",col("col1"),lit(0.25)));//compile
error

//compile error because callUdf() takes String and Column* as arguments.

Please guide. Thanks much.

On Mon, Oct 12, 2015 at 11:44 PM, Ted Yu <yuzhihong@gmail.com> wrote:

> Using spark-shell, I did the following exercise (master branch) :
>
>
> SQL context available as sqlContext.
>
> scala> val df = Seq(("id1", 1), ("id2", 4), ("id3", 5)).toDF("id", "value")
> df: org.apache.spark.sql.DataFrame = [id: string, value: int]
>
> scala> sqlContext.udf.register("simpleUDF", (v: Int, cnst: Int) => v * v +
> cnst)
> res0: org.apache.spark.sql.UserDefinedFunction =
> UserDefinedFunction(<function2>,IntegerType,List())
>
> scala> df.select($"id", callUDF("simpleUDF", $"value", lit(25))).show()
> +---+--------------------+
> | id|'simpleUDF(value,25)|
> +---+--------------------+
> |id1|                  26|
> |id2|                  41|
> |id3|                  50|
> +---+--------------------+
>
> Which Spark release are you using ?
>
> Can you pastebin the full stack trace where you got the error ?
>
> Cheers
>
> On Fri, Oct 9, 2015 at 1:09 PM, Umesh Kacha <umesh.kacha@gmail.com> wrote:
>
>> I have a doubt Michael I tried to use callUDF in  the following code it
>> does not work.
>>
>> sourceFrame.agg(callUdf("percentile_approx",col("myCol"),lit(0.25)))
>>
>> Above code does not compile because callUdf() takes only two arguments
>> function name in String and Column class type. Please guide.
>>
>> On Sat, Oct 10, 2015 at 1:29 AM, Umesh Kacha <umesh.kacha@gmail.com>
>> wrote:
>>
>>> thanks much Michael let me try.
>>>
>>> On Sat, Oct 10, 2015 at 1:20 AM, Michael Armbrust <
>>> michael@databricks.com> wrote:
>>>
>>>> This is confusing because I made a typo...
>>>>
>>>> callUDF("percentile_approx", col("mycol"), lit(0.25))
>>>>
>>>> The first argument is the name of the UDF, all other arguments need to
>>>> be columns that are passed in as arguments.  lit is just saying to make a
>>>> literal column that always has the value 0.25.
>>>>
>>>> On Fri, Oct 9, 2015 at 12:16 PM, <Saif.A.Ellafi@wellsfargo.com> wrote:
>>>>
>>>>> Yes but I mean, this is rather curious. How is def lit(literal:Any)
>>>>> --> becomes a percentile function lit(25)
>>>>>
>>>>>
>>>>>
>>>>> Thanks for clarification
>>>>>
>>>>> Saif
>>>>>
>>>>>
>>>>>
>>>>> *From:* Umesh Kacha [mailto:umesh.kacha@gmail.com]
>>>>> *Sent:* Friday, October 09, 2015 4:10 PM
>>>>> *To:* Ellafi, Saif A.
>>>>> *Cc:* Michael Armbrust; user
>>>>>
>>>>> *Subject:* Re: How to calculate percentile of a column of DataFrame?
>>>>>
>>>>>
>>>>>
>>>>> I found it in 1.3 documentation lit says something else not percent
>>>>>
>>>>>
>>>>>
>>>>> public static Column <https://spark.apache.org/docs/1.3.1/api/java/org/apache/spark/sql/Column.html>
lit(Object literal)
>>>>>
>>>>> Creates a Column
>>>>> <https://spark.apache.org/docs/1.3.1/api/java/org/apache/spark/sql/Column.html>
of
>>>>> literal value.
>>>>>
>>>>> The passed in object is returned directly if it is already a Column
>>>>> <https://spark.apache.org/docs/1.3.1/api/java/org/apache/spark/sql/Column.html>.
>>>>> If the object is a Scala Symbol, it is converted into a Column
>>>>> <https://spark.apache.org/docs/1.3.1/api/java/org/apache/spark/sql/Column.html>
also.
>>>>> Otherwise, a new Column
>>>>> <https://spark.apache.org/docs/1.3.1/api/java/org/apache/spark/sql/Column.html>
is
>>>>> created to represent the literal value.
>>>>>
>>>>>
>>>>>
>>>>> On Sat, Oct 10, 2015 at 12:39 AM, <Saif.A.Ellafi@wellsfargo.com>
>>>>> wrote:
>>>>>
>>>>> Where can we find other available functions such as lit() ? I can’t
>>>>> find lit in the api.
>>>>>
>>>>>
>>>>>
>>>>> Thanks
>>>>>
>>>>>
>>>>>
>>>>> *From:* Michael Armbrust [mailto:michael@databricks.com]
>>>>> *Sent:* Friday, October 09, 2015 4:04 PM
>>>>> *To:* unk1102
>>>>> *Cc:* user
>>>>> *Subject:* Re: How to calculate percentile of a column of DataFrame?
>>>>>
>>>>>
>>>>>
>>>>> You can use callUDF(col("mycol"), lit(0.25)) to call hive UDFs from
>>>>> dataframes.
>>>>>
>>>>>
>>>>>
>>>>> On Fri, Oct 9, 2015 at 12:01 PM, unk1102 <umesh.kacha@gmail.com>
>>>>> wrote:
>>>>>
>>>>> Hi how to calculate percentile of a column in a DataFrame? I cant find
>>>>> any
>>>>> percentile_approx function in Spark aggregation functions. For e.g. in
>>>>> Hive
>>>>> we have percentile_approx and we can use it in the following way
>>>>>
>>>>> hiveContext.sql("select percentile_approx("mycol",0.25) from myTable);
>>>>>
>>>>> I can see ntile function but not sure how it is gonna give results
>>>>> same as
>>>>> above query please guide.
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> View this message in context:
>>>>> http://apache-spark-user-list.1001560.n3.nabble.com/How-to-calculate-percentile-of-a-column-of-DataFrame-tp25000.html
>>>>> Sent from the Apache Spark User List mailing list archive at
>>>>> Nabble.com.
>>>>>
>>>>> ---------------------------------------------------------------------
>>>>> To unsubscribe, e-mail: user-unsubscribe@spark.apache.org
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>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>
>

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