ranking

Help explain BM25 algorithm

can anybody please explain to me about this BM25 algorithm presented on wikipedia link text i'm always bad with math, lol. currently im using classic t-idf which isn't quite good. thanks. ...

Using a SQL Ranking Function with a derived column

I am trying to use a SQL Server 2008 Ranking Function on a query sorted by a derived column. Here's an example SELECT table.FirstName, table.LastName, CalculatedValue(table.number) As Points, ROW_NUMBER() OVER (ORDER BY points) AS 'Row Number' FROM table ORDER BY points I always get an error invalid column name "point...

Find largest and second largest element in a range

How do I find the above without removing the largest element and searching again? Is there a more efficient way to do this? It does not matter if the these elements are duplicates. ...

How should I handle "ranked x out of y" data in PostgreSQL?

I have a table that I would like to be able to present "ranked X out of Y" data for. In particular, I'd like to be able to present that data for an individual row in a relatively efficient way (i.e. without selecting every row in the table). The ranking itself is quite simple, it's a straight ORDER BY on a single column in the table. Po...

searching for and ranking results

I'm trying to write a relatively simple algorithm to search for a string on several attributes Given some data: Some data: 1: name: 'Josh', location: 'los angeles' 2: name: 'Josh', location: 'york' search string: "josh york" The results should be [2, 1] because that query string hits the 2nd record twice, and the 1st record once. ...

Oracle: Find previous record for a ranked list of forecasts

Hi I am faced with a difficult problem: I have a table (oracle 9i) of weather forecasts (many 100's of millions of records in size.) whose makeup looks like this: stationid forecastdate forecastinterval forecastcreated forecastvalue --------------------------------------------------------------------------------- varchar (...

PHP Ranking System Array Sort

Hi, I develop a ranking system. I got the following array: [1] => Array ( [botarin - Branding und Kommunikation] => 1 [Raiffeisen Kredit 2 Go] => 2 ) [2] => Array ( [Kindersteckdosen] => 1 [Surf lieber mit bob] => 1 [Lafarge Imageinserate] => 1 [MCG Messecongress Graz Inserat...

MySQL Group By with top N number of each kind

I have a table like this: Rank Letter 1 A 2 A 3 B 4 A 5 C 6 A 7 C 8 C 9 B 10 C And I need the top 2 of each letter ordered by ascending rank: Rank Letter 1 A 2 A 3 B 5 C 7 C 9 B How would I do ...

Do hidden attributes in CSS style table of pages lower the website power?

In CSS style table of website pages I have used a lot of hidden attributes like overflow:hidden and display:none; Does this has effect for SEO? Is this friendly for search engines (SE)? Can it be punished by search engine (SE)? Can hidden attributes in CSS style table of pages lower the website power? ...

In PHP/CodeIgniter how do you calculate Class & Form Rank based on grades for a student?

I have a database table that holds the following grade information for a student: student_id subject_id gpa letter_grade (which is calculated based on gpa, s the best way to do it? ...

What is a "safety variable"?

I was just reading an article about different ranking algorithms. One thing I'm a bit confused about is stumbleupon's algoritm: (Initial stumbler audience / # domain) + ((% stumbler audience / # domain) + organic bonus – nonfriend) – (% stumbler audience + organic bonus) + N N is a "safety variable" so that the assumed al...

Ranking Elements of multiple Lists by their count in Python

I want to rank multiple lists according to their elements how often they appear in each list. Example: list1 = 1,2,3,4 list2 = 4,5,6,7 list3 = 4,1,8,9 result = 4,1,2,3,4,5,6,7,8 (4 is counted three times, 1 two times and the rest once) I've tried the following but i need something more intelligent and something i can do with any ammou...

1 vs 1 vote: calculate ratings (Flickchart.com)

Instead of rating items with grades from 1 to 10, I would like to have 1 vs 1 "fights". Two items are displayed beside each other and you pick the one which you like more. Based on these "fight" results, an algorithm should calculate ratings for each item. You can see this approach on Flickchart.com where movies are rated using this app...

Finding the rank or index of some name in an array returned by query

I am firing a query which returns minimum 1000 rows containing name, amount in order amount desc. I want the index of some name from that array, I don't know how to do it? As I am using Ruby, I use arr.index(name)+1 method which returns the index properly. But I want some MySQL query which gives me only numbers for that particular name....

Mysql - How do I order results by alternating (1,2,3, 1, 2, 3, 1, 2, 3,) rows, is it possible?

I want to order my results by client 1, 2, 3, then again client 1, 2, 3, and so on. Is there a way to do this without using a for loop or making three separate queries? Not only that, but I am working with paginated data so it needs to return x results, but consistently. Any ideas? GROUP BY maybe? client_id project_id project_name ...

Row Rank in a MySQL View

I need to create a view that automatically adds virtual row number in the result. the graph here is totally random all that I want to achieve is the last column to be created dynamically. > +--------+------------+-----+ > | id | variety | num | > +--------+------------+-----+ > | 234 | fuji | 1 | > | 4356 | gala ...

MySQL "ORDER BY" the amount of rows with the same value for a certain column?

I have a table called trends_points, this table has the following columns: id (the unique id of the row) userId (the id of the user that has entered this in the table) term (a word) time (a unix timestamp) Now, I'm trying to run a query on this table which will get the rows in a specific time frame ordered by how many times the colum...

How does twitter's trending topics algorithm decide which words to extract from tweets?

I saw this question, which focuses on the "Brittney Spears" problem. But I have a bit of a different question. How does the algorithm determine which words or phrases need to be ranked? For instance, if I send out a tweet that says "Michael Jackson died", how does it know to pull out "Michael Jackson" but not "died"? Or suppose that ...

Retrieving a set of all Nth children

The situation: MySQL 5.0 2 tables 1-to-many parent-child foreign key relationship (A.ID = B.PARENT_ID) What's needed: A SELECT query that yields the set of all the Nth children (sorted by their IDs) Also need a form for use in UPDATE Example: Table B | ID | PARENT_ID | ------------------ | 1 | 1 | | 2 | 1 | | ...

mySQL updating but also not updating

I am writing in mySQL/PHP, but have this problem I cannot get my head around. This one PHP script contains two SQL statements. What I am trying to do is update a sports league table (a SQL table called tblrank - which contains many league tables, separated by TableID), and to indicate if the team has gone up or down since the last time i...