pyspark - Applying User Function to Entire Spark DataFrame column -


spark dataframe schema: 

in [177]: testtbl.printschema() root  |-- date: long (nullable = true)  |-- close: double (nullable = true)  |-- volume: double (nullable = true)

i wish apply scalar-valued function column of testtbl. suppose wish calculate average of 'close' column. rdd 

rdd.fold(0, lambda x,y: x+y)

but testtbl.close not rdd,, column object limited functionality. rows of testtbl rdds, columns not. how apply add, or user function single column?

if want apply function entire column, have execute aggregation operation column.

for instance imagine want compute sum of values in column values. though, df not aggregated data, valid apply aggregated functions dataframes.

from pyspark.sql.functions import *  df = sc.parallelize([(1,), (2,), (3,)]).todf(["values"]) df.agg(sum("values").alias("sum")).show()  +---+ |sum| +---+ |  6| +---+

you can find example in pyspark's aggregation documentation.

for second part of question. can create user defined aggregated function, if i'm right applicable scala.


Comments

Post a Comment

Popular posts from this blog

jOOQ update returning clause with Oracle -

according http://www.jooq.org/doc/3.8/manual/sql-building/sql-statements/update-statement/ jooq doesn't support returning clause in update statements databases except firebird , postgres. does know, still correct oracle jooq? according oracle's documentation, oracle db supports returning clase delete, insert, or update statements. incorrect manual you're right - manual wrong , should fixed: https://github.com/jooq/jooq/issues/5470 single row update returning jooq 3.8 added support single row update .. returning statements. internally, uses callablestatement , pl/sql block of form: begin update "my_table" set "my_table"."column" = 'xyz' "my_table"."id" = 1 returning "my_table"."id", "my_table"."column" ?, ?; ? := sql%rowcount; end; the relevant issue is: https://github.com/jooq/jooq/issues/5190 multi row update returning a...
Read more

java - Warning equals/hashCode on @Data annotation lombok with inheritance -

i have entity inherits other. on other hand, i'm using lombok project reduce boilerplate code, put @data annotation. annotation @data inheritance produces next warning: generating equals/hashcode implementation without call superclass, though class not extend java.lang.object. if intentional, add '@equalsandhashcode(callsuper=false)' type. is advisable add annotation @equalsandhashcode (callsuper = true) or @equalsandhashcode (callsuper = false) ? if not added, 1 callsuper=false or callsuper=true ? the default value false . 1 if don't specify , ignore warning. yes, recommended add @equalsandhashcode annotation on @data annotated classes extend else object. cannot tell if need true or false , depends on class hierarchy, , need examined on case-by-case basis. however, project or package, can configure in lombok.config call super methods if not direct subclass of object. lombok.equalsandhashcode.callsuper = call for configuration system ...
Read more

java - BasicPathUsageException: Cannot join to attribute of basic type -

i using java 8 jpa (hibernate 5.2.1). have clause works perfectly, until introduce clause make use foreign key table values too. i getting following error: basicpathusageexception: cannot join attribute of basic type i think problem related fact have join table, , not sure how create join using join table. employee - employee_category - category model (employee.java): @manytomany(cascade = cascadetype.all, fetch=fetchtype.eager) @jointable ( name="employee_category", joincolumns={ @joincolumn(name="emp_id", referencedcolumnname="id") }, inversejoincolumns={ @joincolumn(name="cat_id", referencedcolumnname="id") } ) private set<category> categories; model (category.java): @id private string id; jpa when introduce following code, fails error above (i think problem new piece of code): join<t, category> category = from.join("id"); predicates.add(criteriabuilder.like(category....
Read more