group-by

问题 I struggled finding the solution I was looking for in other stackoverflow posts, even though I strongly feel as if it must exist. If it does, please do forward me in the right direction. I am trying to do a pretty standard group by in javascript using sports data. I have the following array of objects: const myData = [ {team: "GSW", pts: 120, ast: 18, reb: 11}, {team: "GSW", pts: 125, ast: 28, reb: 18}, {team: "GSW", pts: 110, ast: 35, reb: 47}, {team: "HOU", pts: 100, ast: 17, reb: 43},

问题 So dask has now been updated to support custom aggregation functions for groupby. (Thanks to the dev team and @chmp for working on this!). I am currently trying to construct a mode function and corresponding count function. Basically what I envision is that mode returns a list, for each grouping, of the most common values for a specific column (ie. [4, 1, 2]). Additionally, there is a corresponding count function that returns the number of instances of those values, ie. 3. Now I am currently

问题 Here is my query - var data = Goaldata.GroupBy(c => c.GoalId).ToList(); This returns a Igrouping object and I want an Iqueryable object which I can directly query to get the data while in this case I have to loop through using a foreach() and then get the data. Is there another way to group by in LINQ which returns directly as a list of Iqueryable or a List as similar to what happens for order by in LINQ. 回答1: The easiest way is probably var data = Goaldata.GroupBy(c => c.GoalId).SelectMany(c

问题 I have a table named forms with the following structure- GROUP | FORM | FILEPATH ==================================== SomeGroup | SomeForm1 | SomePath1 SomeGroup | SomeForm2 | SomePath2 ------------------------------------ I use the following query- SELECT * FROM forms GROUP BY 'GROUP' It returns only the first row- GROUP | FORM | FILEPATH ==================================== SomeGroup | SomeForm1 | SomePath1 ------------------------------------ Shouldn't it return both (or all of it)? Or am

问题 Does anyone know why I am not able to group TotalSales in this query and if so how can I fix this: select coalesce(Author_ID, 'All Authors') as Author_ID , case when Author_ID is null then ' ' else coalesce(Book_ID, 'All Books') end as Book_ID , TotalQuantity , coalesce(TotalSales, 'No Sales') as TotalSales from ( select author_id as Author_ID , book_id as Book_ID , sum(quantity) as TotalQuantity , sum(quantity * order_price) as TotalSales from a_bkinfo.book_authors join a_bkorders.order

问题 I have a query like this: SELECT col1, col2, col3, col4, col5, SUM(col6) AS total FROM table_name WHERE col1 < 99999 GROUP BY 1,2,3,4,5 What does the GROUP BY statement actually accomplish here? The query does not work properly without the comma-separated integers. 回答1: It is equivalent to writing: SELECT col1, col2, col3, col4, col5, SUM(col6) AS total FROM table_name WHERE col1 < 99999 GROUP BY col1, col2, col3, col4, col5 The numbers are the values/columns in the select-list expressed by

问题 I have list with datetime objects. I would like to group by month and add it to the dictionary. So after grouping process I want to have list per month and year. For example: Before grouping [mix below elements] After grouping: 1) January 2015 - 5 elements 2) February 2015 - 2 elements 2) January 2014 - 2 elements I have tried like this: var test = this.myList.GroupBy(x => x.myDate.Month).ToList(); But iI thnink I need to use dictionary. Do you have any ideas how to solve it ? 回答1: Linq

问题 How do i get a random result on group by group_id? its similar like this: Random order for group of rows in mysql here is my fiddle: http://sqlfiddle.com/#!9/1c73d/3 not sure why it always gives me the same result. CREATE TABLE job (`job_id` int, `group_id` int, `user_id` int, `title` varchar(50), `description` varchar(55), `type` tinyint) ; INSERT INTO job (`job_id`, `group_id`, `user_id`, `title`, `description`,`type`) VALUES (1, 1, 100, 'Title 1', 'Text 1', 1), (2, 1, 100, 'Title 2', 'Text

问题 This question already has an answer here : DataFrame / Dataset groupBy behaviour/optimization (1 answer) Closed last year . I know that in RDD's we were discouraged from using groupByKey, and encouraged to use alternatives such as reduceByKey(), and aggregateByKey() since these other methods would reduce first on each partition, and then perform groupByKey() and thus reduces the amount of data being shuffled. Now, my question is if this still applies to Dataset/Dataframe? I was thinking that

问题 I want to be able to concat dataframe results to memory as they go through a function and end up with a whole new dataframe with just the results. How do I do this without having a dataframe all ready created before the function? For example: import pandas as pd import numpy as np rand_df = pd.DataFrame({'A': [ 'x','x','y','y','z','z','z'],'B': np.random.randn(7)}) def myFuncOnDF(df, row): df = df.groupby(['A']).get_group(row).describe() myFuncOnDF(rand_df, 'x') myFuncOnDF(rand_df, 'y')