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• Finding the Reachability Count for all vertices of a DAG

  - by ChrisH

  I am trying to find a fast algorithm with modest space requirements to solve the following problem. For each vertex of a DAG find the sum of its in-degree and out-degree in the DAG's transitive closure. Given this DAG: I expect the following result: Vertex # Reacability Count Reachable Vertices in closure 7 5 (11, 8, 2, 9, 10) 5 4 (11, 2, 9, 10) 3 3 (8, 9, 10) 11 5 (7, 5, 2, 9, 10) 8 3 (7, 3, 9) 2 3 (7, 5, 11) 9 5 (7, 5, 11, 8, 3) 10 4 (7, 5, 11, 3) It seems to me that this should be possible without actually constructing the transitive closure. I haven't been able to find anything on the net that exactly describes this problem. I've got some ideas about how to do this, but I wanted to see what the SO crowd could come up with.

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• Mysql : get data from 2 tables (need help)

  - by quangtruong1985

  Assume that I have 2 tables : members and orders (Mysql) Members : id | name 1 | Lee 2 | brad Orders : id | member_id | status (1: paid, 2: unpaid) | total 1 | 1 | 1 | 1000000 2 | 1 | 1 | 1500000 3 | 1 | 2 | 1300000 4 | 2 | 1 | 3000000 5 | 2 | 2 | 3500000 6 | 2 | 2 | 3300000 I have a sql query : SELECT m.name, COUNT(o.id) as number_of_order, SUM(o.total) as total2 FROM orders o LEFT JOIN members m ON o.member_id=m.id GROUP BY o.member_id which give me this: name | number_of_order | total2 Lee | 3 | 3800000 brad | 3 | 9800000 All that I want is something like this : name | number_of_order | total2 | Paid Unpaid | Paid Unpaid ------------------------------------------------ Lee | 3 | 3800000 | 2 1 | 2500000 1300000 ------------------------------------------------ brad | 3 | 9800000 | 1 2 | 3000000 6800000 ------------------------------------------------ How to make a query that can give me that result? Thanks for your time!

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• Efficient algorithm to generate all solutions of a linear diophantine equation with ai=1

  - by Ben

  I am trying to generate all the solutions for the following equations for a given H. With H=4 : 1) ALL solutions for x_1 + x_2 + x_3 + x_4 =4 2) ALL solutions for x_1 + x_2 + x_3 = 4 3) ALL solutions for x_1 + x_2 = 4 4) ALL solutions for x_1 =4 For my problem, there are always 4 equations to solve (independently from the others). There are a total of 2^(H-1) solutions. For the previous one, here are the solutions : 1) 1 1 1 1 2) 1 1 2 and 1 2 1 and 2 1 1 3) 1 3 and 3 1 and 2 2 4) 4 Here is an R algorithm which solve the problem. library(gtools) H<-4 solutions<-NULL for(i in seq(H)) { res<-permutations(H-i+1,i,repeats.allowed=T) resum<-apply(res,1,sum) id<-which(resum==H) print(paste("solutions with ",i," variables",sep="")) print(res[id,]) } However, this algorithm makes more calculations than needed. I am sure it is possible to go faster. By that, I mean not generating the permutations for which the sums is H Any idea of a better algorithm for a given H ?

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• In Clojure - How do I access keys in a vector of structs

  - by Nick

  I have the following vector of structs: (defstruct #^{:doc "Basic structure for book information."} book :title :authors :price) (def #^{:doc "The top ten Amazon best sellers on 16 Mar 2010."} best-sellers [(struct book "The Big Short" ["Michael Lewis"] 15.09) (struct book "The Help" ["Kathryn Stockett"] 9.50) (struct book "Change Your Prain, Change Your Body" ["Daniel G. Amen M.D."] 14.29) (struct book "Food Rules" ["Michael Pollan"] 5.00) (struct book "Courage and Consequence" ["Karl Rove"] 16.50) (struct book "A Patriot's History of the United States" ["Larry Schweikart","Michael Allen"] 12.00) (struct book "The 48 Laws of Power" ["Robert Greene"] 11.00) (struct book "The Five Thousand Year Leap" ["W. Cleon Skousen","James Michael Pratt","Carlos L Packard","Evan Frederickson"] 10.97) (struct book "Chelsea Chelsea Bang Bang" ["Chelsea Handler"] 14.03) (struct book "The Kind Diet" ["Alicia Silverstone","Neal D. Barnard M.D."] 16.00)]) I would like to sum the prices of all the books in the vector. What I have is the following: (defn get-price "Same as print-book but handling multiple authors on a single book" [ {:keys [title authors price]} ] price) Then I: (reduce + (map get-price best-sellers)) Is there a way of doing this without mapping the "get-price" function over the vector? Or is there an idiomatic way of approaching this problem?

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• JetBrains dotTrace, is it possible to profile source code line by line? else I need another tool

  - by m3ntat

  I am using JetBrains dotTrace, I've profiled my app which is entirely CPU bound. But the results as you walk down the tree don't sum to the level above in the tree, I only see method calls not the body lines of the node in questions method. Is it possible to profile the source code line by line. i.e for one node: SimulatePair() 99.04% --nextUniform() 30.12% --IDCF() 24.08% So the method calls nextUniform + IDCF use 54% of the time in SimulatePair (or 54% total execution time I'm not sure how to read this) regardless what is happening the other 46% of SimulatePair I need some detail on a line by line basis. Any help or alternative tools is much appreciated. Thanks

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• RIA Services and Shared domainlogic??

  - by NPehrsson

  I'm kind of disappointed at Ria Services. I like to work in a domain driven design way, so for example if I'm working with an invoicing system I have an object invoice which will have all methods on it to for example calculate total price from its invoice rows. public decimal Amount { get {return Entries.Sum(x => x.Amount);} } I like to have methods to add a new row to validate in data. public void AddInvoiceRow(Article article, decimal quantity) This is functionality I need on both client and server side. Have I missed something big or is RIA Services not for me? (In the whole, I don't like Silverlight restrictions at all, I mean that we need get; set on every data field we want to transfer for example some fields are not public at all in domain driven design but the technique Silverlight offers forcing us to do bad coding.)

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• Java Future and infinite computation

  - by Chris

  I'm trying to optimize an (infinite) computation algorithm. I have an infinte Sum to calculate ( Summ_{n- infinity} (....) ) My idea was to create several threads using the Future < construct, then combine the intermediate results together. My problem hoewer is that I need a certain precision. So I need to constantly calculate the current result while other threads keep calculating. My question is: Is there some sort of result queue where each finished thread can put its results in, while a main thread can receive those results and then either lets the computation continues or terminate the whole ExecutorService? Any Help would really be appreciated! Thanks!

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• reorder NSArray in objective-c

  - by Jonathan

  I have an NSArray of JSON file locations. There are stored in the user's/app's Document directory and inside each JSON file is a name value. I'm able to retreive the data from JSON files, I don't need help with tht. But I need help on sorting NSArrays I have no idea how I can do that based on a value inside the file, while not being pathetically slow. This is on the iPhone btw. In sum how do I customly reorder NSArrays.

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• How to write a code Newton Raphson code in R involving integration and Bessel function

  - by Ahmed

  I have want to estimate the parameters of the function which involves Bessel function and integration. However, when i tried to run it, i got a message that "Error in f(x, ...) : could not find function "BesselI" ". I don't know to fix it and would appreciate any related proposal. library(Bessel) library(maxLik) library(miscTools) K<-300 f <- function(theta,lambda,u) {exp(-u*theta)*BesselI(2*sqrt(t*u*theta*lambda),1)/u^0.5} F <- function(theta,lambda){integrate(f,0,K,theta=theta,lambda=lambda)$value} tt<-function(theta,lambda){(sqrt(lambda)*exp(-t*lambda)/(2*sqrt(t*theta)))(theta(2*t*lambda-1)*F(theta,lambda)} loglik <- function(param) { theta <- param[1] lambda <- param[2] ll <-sum(log(tt(theta,lambda))) } t<-c(24,220,340,620,550,559,689,543) res <- maxNR(loglik, start=c(0.001,0.0005),print.level=1,tol = 1e-08) summary(res)

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• Most efficient way to extract bit flags

  - by Hallik

  I have these possible bit flags. 1, 2, 4, 8, 16, 64, 128, 256, 512, 2048, 4096, 16384, 32768, 65536 So each number is like a true/false statement on the server side. So if the first 3 items, and only the first 3 items are marked "true" on the server side, the web service will return a 7. Or if all 14 items above are true, I would still get a single number back from the web service which is is the sum of all those numbers. What is the best way to handle the number I get back to find out which items are marked as "true"?

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• How do you get average of sums in SQL (multi-level aggregation)?

  - by paxdiablo

  I have a simplified table xx as follows: rdate date rtime time rid integer rsub integer rval integer primary key on (rdate,rtime,rid,rsub) and I want to get the average (across all times) of the sums (across all ids) of the values. By way of a sample table, I have (with consecutive identical values blanked out for readability): rdate rtime rid rsub rval ------------------------------------- 2010-01-01 00.00.00 1 1 10 2 20 2 1 30 2 40 01.00.00 1 1 50 2 60 2 1 70 2 80 02.00.00 1 1 90 2 100 2010-01-02 00.00.00 1 1 999 I can get the sums I want with: select rdate,rtime,rid, sum(rval) as rsum from xx where rdate = '2010-06-01' group by rdate,rtime,rid which gives me: rdate rtime rid rsum ------------------------------- 2010-01-01 00.00.00 1 30 (10+20) 2 70 (30+40) 01.00.00 1 110 (50+60) 2 150 (70+80) 02.00.00 1 190 (90+100) as expected. Now what I want is the query that will also average those values across the time dimension, giving me: rdate rtime ravgsum ---------------------------- 2010-01-01 00.00.00 50 ((30+70)/2) 01.00.00 130 ((110+150)/2) 02.00.00 190 ((190)/1) I'm using DB2 for z/OS but I'd prefer standard SQL if possible.

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• Most efficient way to solve system of equations involving the digamma function?

  - by Neil G

  What is the most efficient way to solve system of equations involving the digamma function? I have a vector v and I want to solve for a vector w such that for all i: digamma(sum(w)) - digamma(w_i) = v_i and w_i 0 I found the gsl function gsl_sf_psi, which is the digamma function. Is there an identity I can use to reduce the equations? Is my best bet to use a solver? I am using C++0x; which solver is easiest to use and fast?

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• Any way to do slanted/diagonal mouseovers via css/javascript?

  - by cksubs

  Hi, I have a box built via html borders. I want to connect the bottom left corner to the top right corner with a diagonal line. Either with html/css or by using a background image, doesn't matter. I'll figure that part out later. ------ - /- - / - - / - -/---- Here's the tricky part: I want a different thing to happen depending on which side of the line the mouse is hovering over. I'll do something like make some text visible or change the background color. Is that possible in web programing? I've thought of doing a "Riemann sum" type calculation with a bunch of invisible divs. Any easier way? Thanks!

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• Confusion Matrix with number of classified/misclassified instances on it (Python/Matplotlib)

  - by Pinkie

  I am plotting a confusion matrix with matplotlib with the following code: from numpy import * import matplotlib.pyplot as plt from pylab import * conf_arr = [[33,2,0,0,0,0,0,0,0,1,3], [3,31,0,0,0,0,0,0,0,0,0], [0,4,41,0,0,0,0,0,0,0,1], [0,1,0,30,0,6,0,0,0,0,1], [0,0,0,0,38,10,0,0,0,0,0], [0,0,0,3,1,39,0,0,0,0,4], [0,2,2,0,4,1,31,0,0,0,2], [0,1,0,0,0,0,0,36,0,2,0], [0,0,0,0,0,0,1,5,37,5,1], [3,0,0,0,0,0,0,0,0,39,0], [0,0,0,0,0,0,0,0,0,0,38] ] norm_conf = [] for i in conf_arr: a = 0 tmp_arr = [] a = sum(i,0) for j in i: tmp_arr.append(float(j)/float(a)) norm_conf.append(tmp_arr) plt.clf() fig = plt.figure() ax = fig.add_subplot(111) res = ax.imshow(array(norm_conf), cmap=cm.jet, interpolation='nearest') cb = fig.colorbar(res) savefig("confmat.png", format="png") But I want to the confusion matrix to show the numbers on it like this graphic (the right one): http://i48.tinypic.com/2e30kup.jpg How can I plot the conf_arr on the graphic?

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• mysql query: SELECT DISTINCT column1, GROUP BY column2

  - by Adam

  Right now I have the following query: SELECT name, COUNT(name), time, price, ip, SUM(price) FROM tablename WHERE time >= $yesterday AND time <$today GROUP BY name And what I'd like to do is add a DISTINCT by column 'ip', i.e. SELECT DISTINCT ip FROM tablename So my final output would be all the columns, from all the rows that where time is today, grouped by name (with name count for each repeating name) and no duplicate ip addresses. What should my query look like? (or alternatively, how can I add the missing filter to the output with php)? Thanks in advance.

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• how to get group total in self refrenced data in data table ?

  - by Nikhil Vaghela

  I have three columns in my data table. 1) ProductID 2) ProductParentID 3) ProductTotal ProductID and ProductParentID are self refrencing columns where i can set parent child relationship and get child rows based on my relationship. Let us say i have following data Product1     Product11     Product12     Product13         Product131         Product132         Product133 Product2     Product21     Product22     Product23 Next to above hierarchy in Product total column what i want is total of each child rows and sum of those child rows product total should be rolled up to it parent product. E.g if Product 131 total is 10,Product 13 total is 15 and Product 133 total is 5 then the product 13 total should be 30. The logic should work for n number of self hierarchy. Is there any functionality in data table itself where i can achieve this without iterating through each row and do it manually ? Thanks.

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• Communication between Page and User Controls

  - by Narmatha Balasundaram

  I have a main page that has multiple user controls on it. All the user controls have static text and some data to be retrieved from the DB. The aysnchronous DB call is clubbed at the page level and one call is made to avoid multiple calls (in the different user controls) to get the same data. I want the page and user controls to load initially with the static text and later refresh the contents obtained from the server. To sum it all up, Page Loads = Asyn calls fired on page load = Data received back from the server (XML/text/whatever) = User controls to load with this data using AJAX. What methods do I have to let the user controls know that I have the data from the server and they need to update with this data?

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• What is the most efficient way to solve system of equations containing the digamma function?

  - by Neil G

  What is the most efficient way to solve system of equations involving the digamma function? I have a vector v and I want to solve for a vector w such that for all i: digamma(sum(w)) - digamma(w_i) = v_i and w_i 0 I found the gsl function gsl_sf_psi, which is the digamma function (calculated using some kind of series.) Is there an identity I can use to reduce the equations? Is my best bet to use a solver? I am using C++0x; which solver is easiest to use and fast?

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• Complex queries using Rails query language

  - by Daniel Johnson

  I have a query used for statistical purposes. It breaks down the number of users that have logged-in a given number of times. User has_many installations and installation has a login_count. select total_login as 'logins', count(*) as `users` from (select u.user_id, sum(login_count) as total_login from user u inner join installation i on u.user_id = i.user_id group by u.user_id) g group by total_login; +--------+-------+ | logins | users | +--------+-------+ | 2 | 3 | | 6 | 7 | | 10 | 2 | | 19 | 1 | +--------+-------+ Is there some elegant ActiveRecord style find to obtain this same information? Ideally as a hash collection of logins and users: { 2=>3, 6=>7, ... I know I can use sql directly but wanted to know how this could be solved in rails 3.

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• Why does Sql Server recommends creating an index when it already exist?

  - by Pierre-Alain Vigeant

  I ran a very basic query against one of our table and I noticed that the execution plan query processor is recommending that we create an index on a column The query is SELECT SUM(DATALENGTH(Data)) FROM Item WHERE Namespace = 'http://some_url/some_namespace/' After running, I get the following message // The Query Processor estimates that implementing the following index could improve the query cost by 96.7211%. CREATE NONCLUSTERED INDEX [<Name of Missing Index, sysname,>] ON [dbo].[Item] ([Namespace]) My problem is that I already have such index on that column: CREATE NONCLUSTERED INDEX [IX_ItemNamespace] ON [dbo].[Item] ( [Namespace] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] Why is Sql Server recommending me to create such index when it already exist?

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• T-SQL aggregate function Logical error

  - by Yoda

  Hi Guys, Ok I have a data table containing duplicate Reciept numbers and a transaction value for each record, I need to simply list the total for each unique Reciept number, this is obviously a simple problem but I am missing something. Any help is much appriciated > SELECT Gf_Receipt_number AS Reciept, > SUM (Gf_Amount) AS Total FROM > [TestP].[dbo].[Gf] WHERE > Gf_Receipt_number IS NOT NULL GROUP > BY Gf_Amount Would probably help to mention the the error I am recieving is: Column 'TestP.dbo.Gf.Gf_Receipt_number' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

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• How to get accuracy memory usage on iphone device.

  - by Favo Yang

  I want to output accuracy memory usage on iphone device, the method I used was taking from, http://landonf.bikemonkey.org/code/iphone/Determining%5FAvailable%5FMemory.20081203.html natural_t mem_used = (vm_stat.active_count + vm_stat.inactive_count + vm_stat.wire_count) * pagesize; natural_t mem_free = vm_stat.free_count * pagesize; natural_t mem_total = mem_used + mem_free; The issue is that the total value is always changed after testing on device! used: 60200.0KB free: 2740.0KB total: 62940.0KB used: 53156.0KB free: 2524.0KB total: 55680.0KB used: 52500.0KB free: 2544.0KB total: 55044.0KB Have a look for the function implementation, it already sum active, inactive, wire and free pages, is there anything I missing here?

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• Python KMeans clustering words

  - by sadawd

  Dear Everyone I am interested to perform kmeans clustering on a list of words with the distance measure being Leveshtein. 1) I know there are a lot of frameworks out there, including scipy and orange that has a kmeans implementation. However they all require some sort of vector as the data which doesn't really fit me. 2) I need a good clustering implementation. I looked at python-clustering and realize that it doesn't a) return the sum of all the distance to each centroid, and b) it doesn't have any sort of iteration limit or cut off which ensures the quality of the clustering. python-clustering and the clustering algorithm on daniweb doesn't really work for me. Can someone find me a good lib? Google hasn't been my friend

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• Determine Click-thru Percentage With PHP

  - by Lea

  Hi all, I am currently working on a small sponsorship application(PHP/MySql) for my personal blog, and am almost finish, but I am stuck on how to calculate the click-thru rate of my sponsors campaigns. I was always terrible with working out percentages, so any practical help would be appreciated. The data is stored in the DB as simple numbers.. So as expected, when a page refreshes, or a sponsors ad is clicked, the data updates with an incrementation of 1. So using these values...say $clicks and $impressions, how would I determine the click-thru rate? What would be the sum I would use to calculate? An example function would really be appreciated. Kind Regards, Lea

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• Matlab: Adding symbols to figure

  - by niko

  Hi, Below is the user interface I have created to simulate LDPC coding and decoding The code sequence is decoded iteratively by passing values between the left and right nodes through the connections. The first thing it would be good to add in order to improve visualization is to add arrows to the connections in the direction of passing values. The alternative is to draw a bigger arrow at the top of the connection showing the direction. Another thing I would like to do is displaying the current mathematical operation below the connection (in this example c * H'). What I don't know how to do is displaying special characters and mathematical symbols and other kinds of text such as subscript and superscript in the figure (for example sum sign and subscript "T" instead of sign ="'" to indicate transposed matrix). I would be very thankful if anyone could point to any useful resources for the questions above or show the solution. Thank you.

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