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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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• Keyboard input: how to separate keycodes received from user

  - by Iulian Serbanoiu

  Hello, I am writing an application involving user input from the keyboard. For doing it I use this way of reading the input: #include <stdio.h> #include <termios.h> #include <unistd.h> int mygetch( ) { struct termios oldt, newt; int ch; tcgetattr( STDIN_FILENO, &oldt ); newt = oldt; newt.c_lflag &= ~( ICANON | ECHO ); tcsetattr( STDIN_FILENO, TCSANOW, &newt ); ch = getchar(); tcsetattr( STDIN_FILENO, TCSANOW, &oldt ); return ch; } int main(void) { int c; do{ c = mygetch(); printf("%d\n",c); }while(c!='q'); return 0; } Everyting works fine for letters digits,tabs but when hiting DEL, LEFT, CTRL+LEFT, F8 (and others) I receive not one but 3,4,5 or even 6 characters. The question is: Is is possible to make a separation of these characters (to actually know that I only hit one key or key combination). What I would like is to have a function to return a single integer value for any type of input (letter, digit, F1-F12, DEl, PGUP, PGDOWN, CTRL+A, CTRL+ALT+A, ALT+LEFT, etc). Is this possible? I'm interested in an idea to to this, the language doesn't matter much, though I'd prefer perl or c. Thanks, Iulian

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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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• 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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• 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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• Tool for generating flat files from SQL objects dynamically

  - by Fabio Gouw

  Hello! I'm looking for a tool or component that generates flat files given a SQL Server's query result (from a stored procedure or a SELECT * over a table or view). This will be a batch process which runs every day, and every day a new file is created. I could use SQL Server Integration Services (DTS), but I have a mandatory requirement: the output of the file need to be dynamic. If a new column is added in my query result, the file must have this new column too, without having to modify my SSIS package. If a column is removed, then the flat file no longer will have it. I’ve tried to do this with SSIS, but when I create a new package I need to specify the number of columns. Another requirement is configuring the format of the output, depending on the data type of the column. If it’s a datetime, the format needs to be YYYY-MM-DD. If it’s a float, then I need to use 2 decimal digits, and so on. Does anyone know a tool that does this job? Thanks

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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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• 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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• 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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• Stop Excel from changing cell contents, ever

  - by Enable Manual-Correct

  I work with card numbers, like credit card and ID numbers. We do not do any calculations with card numbers, obviously. They are "text." I format them as text, I type them like text. I know how that works. Excel doesn't care. 16 digit card numbers get their last digit turned into a zero, changed into scientific notation, stupid stuff that I did not tell Excel to do. I need to do things like Find/Remove spaces from cells in files downloaded from our currently imperfect web-system. The system sends me files with 16 digit numbers, cells formatted as text, but due to bugs there are spaces at the end. I do Find/Remove all spaces and all my card numbers are transformed into scientific notation and the last digit turned into a 0. THEY ARE TEXT, they are formatted as text, I yelled into the screen that they are text, why does Excel refuse to acknowledge that they are text? (I would rather find a way to stop Excel's action than find a way to tell our programmers to put an apostrophe in every cell) How do I make it so that Excel just STOPS doing anything that I didn't tell it to do? Or at least stop it from doing anything to numbers it doesn't like. Maybe I can write a macro for whenever it discovers "Uhoh I should change that number to something different!" I'll make it format that cell to text a thousand times instead. Give me an error when I try calculating with a number larger than 15 digits, make my computer explode violently, that's fine. Just stop changing the numbers. Is it possible? I have many thousands of numbers that need changing in many different scenarios. I just want to stop it from trying to help. I can't understand why that would be difficult. I have 2007, but answers for other versions would be great as well. Thank you!

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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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• Is there a Boost (or other common lib) type for matrices with string keys?

  - by mohawkjohn

  I have a dense matrix where the indices correspond to genes. While gene identifiers are often integers, they are not contiguous integers. They could be strings instead, too. I suppose I could use a boost sparse matrix of some sort with integer keys, and it wouldn't matter if they're contiguous. Or would this still occupy a great deal of space, particularly if some genes have identifiers that are nine digits? Further, I am concerned that sparse storage is not appropriate, since this is an all-by-all matrix (there will be a distance in each and every cell, provided the gene exists). I'm unlikely to need to perform any matrix operations (e.g., matrix multiplication). I will need to pull vectors out of the matrix (slices). It seems like the best type of matrix would be keyed by a Boost unordered_map (a hash map), or perhaps even simply an STL map. Am I looking at this the wrong way? Do I really need to roll my own? I thought I saw such a class somewhere before. Thanks!

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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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• 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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• Batch update records in Grails

  - by UltraVi01

  I have to calculate a "total" for each user based on individual actions -- that is, a User hasMany Actions and each Action has a point. So I need to basically get a sum of all the points on all the actions. Actions are added and subtracted regularly. Since this can be a rather heavy operation, it's not feasible that I execute the "total" each time I need it. Therefore, I am thinking of running the operation once a day for each user and storing the total points on the User as an int. Because I have thousands of users, I am trying to figure out the best way to do this. Should I basically iterate through all the users and call User.save() each time, or is there some kind of batch update mechanism I can use in Grails / GORM?

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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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• Performance of Java matrix math libraries?

  - by dfrankow

  We are computing something whose runtime is bound by matrix operations. (Some details below if interested.) This experience prompted the following question: Do folk have experience with the performance of Java libraries for matrix math (e.g., multiply, inverse, etc.)? For example: JAMA: http://math.nist.gov/javanumerics/jama/ COLT: http://acs.lbl.gov/~hoschek/colt/ Apache commons math: http://commons.apache.org/math/ I searched and found nothing. Details of our speed comparison: We are using Intel FORTRAN (ifort (IFORT) 10.1 20070913). We have reimplemented it in Java (1.6) using Apache commons math 1.2 matrix ops, and it agrees to all of its digits of accuracy. (We have reasons for wanting it in Java.) (Java doubles, Fortran real*8). Fortran: 6 minutes, Java 33 minutes, same machine. jvisualm profiling shows much time spent in RealMatrixImpl.{getEntry,isValidCoordinate} (which appear to be gone in unreleased Apache commons math 2.0, but 2.0 is no faster). Fortran is using Atlas BLAS routines (dpotrf, etc.). Obviously this could depend on our code in each language, but we believe most of the time is in equivalent matrix operations. In several other computations that do not involve libraries, Java has not been much slower, and sometimes much faster.

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• Python multiprocessing doesn't play nicely with uuid.uuid4().

  - by yig

  I'm trying to generate a uuid for a filename, and I'm also using the multiprocessing module. Unpleasantly, all of my uuids end up exactly the same. Here is a small example: import multiprocessing import uuid def get_uuid( a ): ## Doesn't help to cycle through a bunch. #for i in xrange(10): uuid.uuid4() ## Doesn't help to reload the module. #reload( uuid ) ## Doesn't help to load it at the last minute. ## (I simultaneously comment out the module-level import). #import uuid ## uuid1() does work, but it differs only in the first 8 characters and includes identifying information about the computer. #return uuid.uuid1() return uuid.uuid4() def main(): pool = multiprocessing.Pool( 20 ) uuids = pool.map( get_uuid, range( 20 ) ) for id in uuids: print id if __name__ == '__main__': main() I peeked into uuid.py's code, and it seems to depending-on-the-platform use some OS-level routines for randomness, so I'm stumped as to a python-level solution (to do something like reload the uuid module or choose a new random seed). I could use uuid.uuid1(), but only 8 digits differ and I think there are derived exclusively from the time, which seems dangerous especially given that I'm multiprocessing (so the code could be executing at exactly the same time). Is there some Wisdom out there about this issue?

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• Which are your favorite programming language gadgets?

  - by FerranB

  There are some gadgets/features for programming languages that I like a lot because they save a lot of coding or simply because they are magical or nice. Some of my favorites are: C++ increment/decrement operator: my_array[++c]; C++ assign and sum or substract (...): a += b C# yield return: yield return 1; C# foreach: foreach (MyClass x in MyCollection) PLSQL for loop: for c in (select col1, col2 from mytable) PLSQL pipe row: for i in 1..x loop pipe row(i); end loop; Python Array access operator: a[:1] PLSQL ref cursors. Which are yours?

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• difference between a lexical, morphological and semantic mistakes?

  - by AnH

  Hi there, I just want to make sure that I understood the differences between a lexical, morphological and semantic mistakes correctly. If am not mistaken semantic mistakes deal with problems concerning meanings, for example writing a sentence that is correct grammar wise but doesn't make any sense is a semantic mistake, morphological mistakes deals more or less on how the word should look like, for example childrenS is a morphological mistake, so that leaves lexical mistakes, what are those exactly?? can someone sum up the differences between those 3 mistakes please so that I may know for sure that I got them down correctly? Thank you in advance

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• Where to execute extra logic for linq to entities query?

  - by Inez

  Let say that I want to populate a list of CustomerViewModel which are built based on Customer Entity Framework model with some fields (like Balance) calculated separately. Below I have code which works for lists - it is implemented in my service layer, but also I want to execute this code when I just get one item from the database and execute is as well in different services where I'm accessing Customers data as well. How should I do this to ensure performance but to to not duplicate code - the one for calculating Balance? public List<CustomerViewModel> GetCustomerViewModelList() { IQueryable<CustomerViewModel> list = from k in _customerRepository.List() select new CustomerViewModel { Id = k.Id, Name = k.Name, Balance = k.Event.Where(z => z.EventType == (int) EventTypes.Income).Sum(z => z.Amount) }; return list.ToList(); }

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• password validator using RegExp in Flex

  - by kalyaniRavi

  I have seen several examples in Flex for passowrd validator using RegExp. But every where the validation is happend for single validation. I have a requirement, like password validations like • At least one Upper case letter • At least one numeric character • At least one special character such as @, #, $, etc. • At least one Lower case letter • password lenght minimum 6 digits • password cannot be same as user name Can anyone provide me a code for this..? I have the code only for checking the password is valid or not . check the below code. MXML CODE <mx:FormItem label="Username:" x="83" y="96" width="66"> </mx:FormItem> <mx:FormItem label="Password:" x="88" y="123" width="61"> </mx:FormItem> <mx:Button label="Login" id="btnLogin" tabIndex="2" click="login();" enabled="{formIsValid}" x="327" y="162" width="84"/> <mx:TextInput id="txtPassword" displayAsPassword="true" change="validateForm(event);" x="152" y="121" width="217"/> <mx:TextInput id="txtUserId" change="validateForm(event);" x="152" y="94" width="217"/> AS Code: private function validateForm(event:Event):void { focussedFormControl = event.target as DisplayObject; formIsValid = true; formIsEmpty = (txtUserId.text == "" && txtPassword.text == ""); validate(strVUserId); validate(strVPassword); } private function validate(validator:Validator):Boolean { var validatorSource:DisplayObject = validator.source as DisplayObject; var suppressEvents:Boolean = (validatorSource != focussedFormControl); var event:ValidationResultEvent = validator.validate(null, suppressEvents); var currentControlIsValid:Boolean = (event.type == ValidationResultEvent.VALID); formIsValid = formIsValid && currentControlIsValid; return currentControlIsValid; }

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• mySQL Left Join on multiple tables with conditions

  - by Jarrod

  Hi, I have a problem. I have 4 tables: Invoice_Payment, Invoice, Client, and Calendar Basically, I have the below query, which works well, except, months with no date_due don't return. I.E only months with a date_due will be returned. I think I have to use a left join and join the calendar table with something like: LEFT JOIN Calendar ON Invoice_Payments.date_paid = Calendar.date_field. But I'm having no luck SELECT MONTHNAME(Invoice_Payments.date_paid) as month, SUM(Invoice_Payments.paid_amount) AS total FROM Invoice, Client, Invoice_Payments WHERE Client.registered_id = 1 AND Client.id = Invoice.client_id And Invoice.id = Invoice_Payments.invoice_id AND date_paid IS NOT NULL GROUP BY YEAR(Invoice_Payments.date_paid), MONTH(Invoice_Payments.date_paid) Any help appreciated.

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