case

问题 I have a variable in a dataframe where one of the fields typically has 7-8 values. I want to collpase them 3 or 4 new categories within a new variable within the dataframe. What is the best approach? I would use a CASE statement if I were in a SQL-like tool but not sure how to attack this in R. Any help you can provide will be much appreciated! 回答1: case_when() , which was added to dplyr in May 2016, solves this problem in a manner similar to memisc::cases() . For example: library(dplyr)

问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 2 years ago . I wanna make a grpah with many nodes to force kruskal algorithm in worst case scenario. What kind of graph should it be ? I im stuck . 回答1: Supposing you are implementing kruskal algorithm with dijoint sets, and sorting the edges with a stable and "fast" algorithm you will have O

问题 I am looking for a quick way to do SELECT IFNULL(columna, columnb) FROM mytable (I have dozens of columns and don't want to write a case for each of them) 回答1: You can also use the standard COALESCE keyword, which allows you to pass it multiple parameters: SELECT COALESCE(columna, columnb, ..., columnz) FROM mytable COALESCE keyword documentation 回答2: just found out: SELECT nvl(columna, columnb) FROM mytable http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions105.htm 来源： https:/

问题 This question already has answers here : “CASE” statement within “WHERE” clause in SQL Server 2008 (11 answers) Closed 2 years ago . I am trying to add case statement to where condition in a query. My query looks like below- select * from table_name where if(id==1) then col1 = 0 else col1 is null As shown in above query I want to add col1 = 0 in where condition if id-==0 else I want col1 is null in where condition. I tried select * from table_name where case id =1 then (col1 = 0) else col1 is

问题 Im creating customizable product attributes in a web store - each attribute can have different type of data, each data type is stored in a separate column using corresponding mysql datatype. I Have a query like: SELECT products.id AS id, products.sku AS sku, products.name AS name, products.url_key AS url_key, attributes.name AS attribute, CASE WHEN `attribute_types`.`type` = 'text' THEN product_attribute_values.value_text WHEN `attribute_types`.`type` = 'float' THEN product_attribute_values

问题 I'm trying to assign a different column to a sum depending on the dates. Here's what I have: SELECT SUM(amount) CASE WHEN date BETWEEN '1/1/13' AND '1/1/14' THEN Last_yr_tot WHEN date BETWEEN '1/1/14' AND 'now' THEN YTD My entire query. select fd.location_cd ,round(sum(case when fd.fs_dt between '1/1/13' and '12/31/13' then amount else 0 end)::numeric, 0) as Last_yr ,round(sum(case when fd.fs_dt between '1/1/14' and current_date then amount else 0 end)::numeric, 0) as YTD ,round(sum(case when

问题 I have a query that I need to write. Lab assistants will enter the information for students coming to the lab for help. the field are: Visit_ID, Student_ID, Visit_Date, Time_In, Time_Out, Course, Asst_ID. There are 3 sessions for time_in entry Session 1 9-12 Session 2 12-3 Session 3 3-6 The query needs to determine which session on the current day had the most visitors. This is what I have so far: with cte as ( select case when cast(Time_In as time) >'12:00:00' and cast(Time_In as time) <='15

问题 I have two VIEWS where data is represented as below: VIEW 1 | username | function | level | location | |:-----------|------------:|:------------:| :-------------:| | John | Operation | Country | United Kingdom | | John | Operation | Area | South West | | John | Operation | Shop | 0001 | VIEW 2 | shop | region | country | area | |:-----------|------------:|:---------------:| :-------------:| | 1200 | u1 | United Kingdom | West | | 1201 | u2 | United Kingdom | West | | 1000 | f1 | France |

问题 This will work fine in MySQL 5: SELECT INSTR(foo, 'Bar') as foobar FROM Table ORDER BY CASE WHEN foobar = 1 THEN foo END DESC; Bu in MySQL 4, I get the error: ERROR 1054 (42S22): Unknown column 'foobar' in 'order clause' However, if I change the clause to this, it will work on both versions: SELECT INSTR(foo, 'Bar') as foobar FROM Table ORDER BY CASE WHEN INSTR(foo, 'Bar') = 1 THEN foo END DESC; To ensure compatibility, do I have to always use the second way? 回答1: because foobar is an alias.

问题 I have a file with a table like this: I have done that my program returns me the values (max, min and mean) from the line of the gene that I'm looking for. Now my goal is the same, but instead of words, the user will print the number of the column. Ego to obtain these values but only from one column. Here there is my code: #!/bin/bash FICHERO="affy.txt" function OPTIONS { echo "_____________OPTIONS_____________" echo "" echo " 1. Select one gene and its test results" echo " 2. Select one