group-by

问题 This question already has answers here : R group by, counting non-NA values (3 answers) Closed last year . Here is my example mydf<-data.frame('col_1'=c('A','A','B','B'), 'col_2'=c(100,NA, 90,30)) I would like to group by col_1 and count not-NA elements in col_2 I would like to do it with dplyr . Here is what I tried after searching SO: mydf %>% group_by(col_1) %>% summarise_each(funs(!is.na(col_2))) mydf %>% group_by(col_1) %>% mutate(non_na_count = length(col_2, na.rm=TRUE)) mydf %>% group

问题 This question already has answers here : R group by, counting non-NA values (3 answers) Closed last year . Here is my example mydf<-data.frame('col_1'=c('A','A','B','B'), 'col_2'=c(100,NA, 90,30)) I would like to group by col_1 and count not-NA elements in col_2 I would like to do it with dplyr . Here is what I tried after searching SO: mydf %>% group_by(col_1) %>% summarise_each(funs(!is.na(col_2))) mydf %>% group_by(col_1) %>% mutate(non_na_count = length(col_2, na.rm=TRUE)) mydf %>% group

问题 For what would be this query in SQL (to find duplicates): SELECT userId, name FROM col GROUP BY userId, name HAVING COUNT(*)>1 I performed this simple query in MongoDB: res = db.col.group({key:{userId:true,name:true}, reduce: function(obj,prev) {prev.count++;}, initial: {count:0}}) I've added a simple Javascript loop to go over the result set, and performed a filter to find all the fields with a count > 1 there, like so: for (i in res) {if (res[i].count>1) printjson(res[i])}; Is there a

问题 I have a problem with a query in Oracle SQL. I have a first_name column in an employees table. I want to group my records according to the first character in first_name . For example, I have 26 records, one with name = 'Alice' , one with name = 'Bob' , and so on down the alphabet for each name's first character. After the query, there should be 26 groups with one employee each. I tried the following, but it's not working: SELECT employee_id, (SUBSTR(first_name,1,1)) AS alpha FROM employees

问题 I am struggling for a few days with this issue and I can't figure out how can I fix it. I would like to group by my table on values 1 , 2 , 3 , 4 , 5 so I have created a temporary table with this values. Now I have to INNER JOIN this table with other tables on a.value = #myTempTable.num . BUT a.value is ntext so I need to CONVERT it what I actually did, but I am getting an error: Conversion failed when converting the varchar value 'simple, ' to data type int. (on line 7) Create table

问题 TABLE: LOAN Loan_no Amount SSS_no Loan_date 7 700.00 0104849222 2010-01-03 8 200.00 0104849222 2010-02-28 9 300.00 0119611199 2010-11-18 10 150.00 3317131410 2012-11-28 11 600.00 0104849222 2011-01-03 14 175.00 3317131410 2012-12-05 15 260.00 3317131410 2013-02-08 16 230.00 0104849222 2013-03-06 17 265.00 0119611199 2011-04-30 18 455.00 3317131410 2013-03-10 DESIRED RESULTS: I would want to retrieve the latest loan availed off by each person (identified by their SSS number). The results

问题 I've been having trouble articulating the differences between ILookup<TKey, TVal> and IGrouping<TKey, TVal>, and am curious if I understand it correctly now. LINQ compounded the issue by producing sequences of IGrouping items while also giving me a ToLookup extension method. So it felt like they were the same until I looked more closely. var q1 = from n in N group n by n.MyKey into g select g; // q1 is IEnumerable<IGrouping<TKey, TVal>> Which is equivalent to: var q2 = N.GroupBy(n => n.MyKey,

问题 Given the following table ' foo ' ID | First Name | Last Name ---------------------------- 67 John Smith ---------------------------- 67 Bill Jacobs What first_name and last_name will the following query return and why? SELECT * FROM foo WHERE ID = 67 GROUP BY ID 回答1: MySQL chooses a row arbitrarily. In practice, commonly used MySQL storage engines return the values from the first row in the group, with respect to the physical storage. create table foo (id serial primary key, category varchar

问题 I'm new to Angular and would like to learn the best way to handle a problem. My goal is to have a reusable means to create group by headers. I created a solution which works, but I think this should be a directive instead of a scope function within my controller, but I'm not sure how to accomplish this, or if a directive is even the right way to go. Any inputs would be greatly appreciated. See my current approach working on jsFiddle In the HTML it's a simple list using ng-repeat where I call

问题 I'm trying to write a MySQL query to get an average value per month, for all months between to given dates. My idea is this: Query, something like SELECT AVG(value1) as avg_value_1, AVG(value2) as avg_value_2, MONTH(save_date) as month, YEAR(save_date) as year FROM myTable WHERE save_date BETWEEN '2009-01-01' AND '2009-07-01' GROUP BY YEAR(save_date), MONTH(save_date) avg_value_1 | avg_value_2 | month | year 5 | 4 | 1 | 2009 2 | 1 | 2 | 2009 7 | 5 | 3 | 2009 0 | 0 | 4 | 2009 <--- 6 | 5 | 5 |