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• Time series in R

  - by Christian Stade-Schuldt

  Hi, I am tracking my body weight in a spread sheet but I want to improve the experience by using R. I was trying to find some information about time series analysis in R but I was not succesful. The data I have here is in the following format: date - weight - body-fat-percentage - water-percentage e.g. 10/08/09 - 84.30 - 18.20 - 55.3 What I want to do plot weight and exponential moving average against time How can I achieve that?

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• What's a good library for parsing mathematical expressions in java?

  - by CSharperWithJava

  I'm an Android Developer and as part of my next app I will need to evaluate a large variety of user created mathematical expressions and equations. I am looking for a good java library that is lightweight and can evaluate mathematical expressions using user defined variables and constants, trig and exponential functions, etc. I've looked around and Jep seems to be popular, but I would like to hear more suggestions, especially from people who have used these libraries before.

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• Signal processing or algorithmic programming for a PLC

  - by james singen smythe

  I have an application that takes voltages and temperatures as analog inputs and does some processing using an algorithm which involves signal processing such as low-pass filtering, exponential smoothing, and other steps which might typically be done in a high-level programming language such as C or C++. I'm curious how I could perform these same steps using a PLC, and in particular, the Allen-Bradley Control-Logix system? It seems to me that the instruction set with ladder logic is too limited for this. Could I perform this using structured text?

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• When should automation begin?

  - by onesith

  I want to start implementing automation. I just don't know if this would be a good use of resource. The application is growing at an exponential rate but i don't know at what point does automation benefits testing. Can you give me reasons why you would automate even though you have manual testers?

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• Parsing numbers at PreviewTextInput

  - by Nitin Chaudhari

  I have a WPF application in which I have a hook at PreviewTextInput, through that I get the currently entered character and I have the string already entered. Given this I need to write the following function : bool ShouldAccept(char newChar,string existingText) existingText can be comma seperated valid numbers(including exponential) and it should just return false when invalid characters are pressed. My code(if else based) currently has a lot of flaws, I wanted to know if there is any smart way to do it.

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• C#: How to replace "-" with " -" only when it's not preceded by "e"?

  - by MaDDoX

  I imagine I should use Regex for that but I still scratch my head a lot about it (and the only similar question I found wasn't exactly my case) so I decided to ask for help. This is the input and expected output: Input: "c-0.68219,-0.0478 -1.01455-0.0441 0.2321e-4,0.43212" Output:"c -0.68219,-0.0478 -1.01455 -0.0441 0.2321e-4,0.43212" Basically I need either commas or spaces as value separators, but I can't break the exponential index (e-4). Maybe do two successive replacements?

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• Is there a shorthand term for O(n log n)?

  - by jemfinch

  We usually have a single-word shorthand for most complexities we encounter in algorithmic analysis: O(1) == "constant" O(log n) == "logarithmic" O(n) == "linear" O(n^2) == "quadratic" O(n^3) == "cubic" O(2^n) == "exponential" We encounter algorithms with O(n log n) complexity with some regularity (think of all the algorithms dominated by sort complexity) but as far as I know, there's no single word we can use in English to refer to that complexity. Is this a gap in my knowledge, or a real gap in our English discourse on computational complexity?

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• SQL SERVER – Weekly Series – Memory Lane – #035

  - by Pinal Dave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 Row Overflow Data Explanation  In SQL Server 2005 one table row can contain more than one varchar(8000) fields. One more thing, the exclusions has exclusions also the limit of each individual column max width of 8000 bytes does not apply to varchar(max), nvarchar(max), varbinary(max), text, image or xml data type columns. Comparison Index Fragmentation, Index De-Fragmentation, Index Rebuild – SQL SERVER 2000 and SQL SERVER 2005 An old but like a gold article. Talks about lots of concepts related to Index and the difference from earlier version to the newer version. I strongly suggest that everyone should read this article just to understand how SQL Server has moved forward with the technology. Improvements in TempDB SQL Server 2005 had come up with quite a lots of improvements and this blog post describes them and explains the same. If you ask me what is my the most favorite article from early career. I must point out to this article as when I wrote this one I personally have learned a lot of new things. Recompile All The Stored Procedure on Specific TableI prefer to recompile all the stored procedure on the table, which has faced mass insert or update. sp_recompiles marks stored procedures to recompile when they execute next time. This blog post explains the same with the help of a script.  2008 SQLAuthority Download – SQL Server Cheatsheet You can download and print this cheat sheet and use it for your personal reference. If you have any suggestions, please let me know and I will see if I can update this SQL Server cheat sheet. Difference Between DBMS and RDBMS What is the difference between DBMS and RDBMS? DBMS – Data Base Management System RDBMS – Relational Data Base Management System or Relational DBMS High Availability – Hot Add Memory Hot Add CPU and Hot Add Memory are extremely interesting features of the SQL Server, however, personally I have not witness them heavily used. These features also have few restriction as well. I blogged about them in detail. 2009 Delete Duplicate Rows I have demonstrated in this blog post how one can identify and delete duplicate rows. Interesting Observation of Logon Trigger On All Servers – Solution The question I put forth in my previous article was – In single login why the trigger fires multiple times; it should be fired only once. I received numerous answers in thread as well as in my MVP private news group. Now, let us discuss the answer for the same. The answer is – It happens because multiple SQL Server services are running as well as intellisense is turned on. Blog post demonstrates how we can do the same with the help of SQL scripts. Management Studio New Features I have selected my favorite 5 features and blogged about it. IntelliSense for Query Editing Multi Server Query Query Editor Regions Object Explorer Enhancements Activity Monitors Maximum Number of Index per Table One of the questions I asked in my user group was – What is the maximum number of Index per table? I received lots of answers to this question but only two answers are correct. Let us now take a look at them in this blog post. 2010 Default Statistics on Column – Automatic Statistics on Column The truth is, Statistics can be in a table even though there is no Index in it. If you have the auto- create and/or auto-update Statistics feature turned on for SQL Server database, Statistics will be automatically created on the Column based on a few conditions. Please read my previously posted article, SQL SERVER – When are Statistics Updated – What triggers Statistics to Update, for the specific conditions when Statistics is updated. 2011 T-SQL Scripts to Find Maximum between Two Numbers In this blog post there are two different scripts listed which demonstrates way to find the maximum number between two numbers. I need your help, which one of the script do you think is the most accurate way to find maximum number? Find Details for Statistics of Whole Database – DMV – T-SQL Script I was recently asked is there a single script which can provide all the necessary details about statistics for any database. This question made me write following script. I was initially planning to use sp_helpstats command but I remembered that this is marked to be deprecated in future. 2012 Introduction to Function SIGN SIGN Function is very fundamental function. It will return the value 1, -1 or 0. If your value is negative it will return you negative -1 and if it is positive it will return you positive +1. Let us start with a simple small example. Template Browser – A Very Important and Useful Feature of SSMS Templates are like a quick cheat sheet or quick reference. Templates are available to create objects like databases, tables, views, indexes, stored procedures, triggers, statistics, and functions. Templates are also available for Analysis Services as well. The template scripts contain parameters to help you customize the code. You can Replace Template Parameters dialog box to insert values into the script. An invalid floating point operation occurred If you run any of the above functions they will give you an error related to invalid floating point. Honestly there is no workaround except passing the function appropriate values. SQRT of a negative number will give you result in real numbers which is not supported at this point of time as well LOG of a negative number is not possible (because logarithm is the inverse function of an exponential function and the exponential function is NEVER negative). Validating Spatial Object with IsValidDetailed Function SQL Server 2012 has introduced the new function IsValidDetailed(). This function has made my life very easy. In simple words, this function will check if the spatial object passed is valid or not. If it is valid it will give information that it is valid. If the spatial object is not valid it will return the answer that it is not valid and the reason for the same. This makes it very easy to debug the issue and make the necessary correction. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Refactoring Part 1 : Intuitive Investments

  - by Wes McClure

  Fear, it’s what turns maintaining applications into a nightmare.  Technology moves on, teams move on, someone is left to operate the application, what was green is now perceived brown.  Eventually the business will evolve and changes will need to be made.  The approach to those changes often dictates the long term viability of the application.  Fear of change, lack of passion and a lack of interest in understanding the domain often leads to a paranoia to do anything that doesn’t involve duct tape and bailing twine.  Don’t get me wrong, those have a place in the short term viability of a project but they don’t have a place in the long term.  Add to it “us versus them” in regards to the original team and those that maintain it, internal politics and other factors and you have a recipe for disaster.  This results in code that quickly becomes unmanageable.  Even the most clever of designs will eventually become sub optimal and debt will amount that exponentially makes changes difficult.  This is where refactoring comes in, and it’s something I’m very passionate about.  Refactoring is about improving the process whereby we make change, it’s an exponential investment in the process of change. Without it we will incur exponential complexity that halts productivity. Investments, especially in the long term, require intuition and reflection.  How can we tackle new development effectively via evolving the original design and paying off debt that has been incurred? The longer we wait to ask and answer this question, the more it will cost us.  Small requests don’t warrant big changes, but realizing when changes now will pay off in the long term, and especially in the short term, is valuable. I have done my fair share of maintaining applications and continuously refactoring as needed, but recently I’ve begun work on a project that hasn’t had much debt, if any, paid down in years.  This is the first in a series of blog posts to try to capture the process which is largely driven by intuition of smaller refactorings from other projects. Signs that refactoring could help: Testability How can decreasing test time not pay dividends? One of the first things I found was that a very important piece often takes 30+ minutes to test.  I can only imagine how much time this has cost historically, but more importantly the time it might cost in the coming weeks: I estimate at least 10-20 hours per person!  This is simply unacceptable for almost any situation.  As it turns out, about 6 hours of working with this part of the application and I was able to cut the time down to under 30 seconds!  In less than the lost time of one week, I was able to fix the problem for all future weeks! If we can’t test fast then we can’t change fast, nor with confidence. Code is used by end users and it’s also used by developers, consider your own needs in terms of the code base.  Adding logic to enable/disable features during testing can help decouple parts of an application and lead to massive improvements.  What exactly is so wrong about test code in real code?  Often, these become features for operators and sometimes end users.  If you cannot run an integration test within a test runner in your IDE, it’s time to refactor. Readability Are variables named meaningfully via a ubiquitous language? Is the code segmented functionally or behaviorally so as to minimize the complexity of any one area? Are aspects properly segmented to avoid confusion (security, logging, transactions, translations, dependency management etc) Is the code declarative (what) or imperative (how)?  What matters, not how.  LINQ is a great abstraction of the what, not how, of collection manipulation.  The Reactive framework is a great example of the what, not how, of managing streams of data. Are constants abstracted and named, or are they just inline? Do people constantly bitch about the code/design? If the code is hard to understand, it will be hard to change with confidence.  It’s a large undertaking if the original designers didn’t pay much attention to readability and as such will never be done to “completion.”  Make sure not to go over board, instead use this as you change an application, not in lieu of changes (like with testability). Complexity Simplicity will never be achieved, it’s highly subjective.  That said, a lot of code can be significantly simplified, tidy it up as you go.  Refactoring will often converge upon a simplification step after enough time, keep an eye out for this. Understandability In the process of changing code, one often gains a better understanding of it.  Refactoring code is a good way to learn how it works.  However, it’s usually best in combination with other reasons, in effect killing two birds with one stone.  Often this is done when readability is poor, in which case understandability is usually poor as well.  In the large undertaking we are making with this legacy application, we will be replacing it.  Therefore, understanding all of its features is important and this refactoring technique will come in very handy. Unused code How can deleting things not help? This is a freebie in refactoring, it’s very easy to detect with modern tools, especially in statically typed languages.  We have VCS for a reason, if in doubt, delete it out (ok that was cheesy)! If you don’t know where to start when refactoring, this is an excellent starting point! Duplication Do not pray and sacrifice to the anti-duplication gods, there are excellent examples where consolidated code is a horrible idea, usually with divergent domains.  That said, mediocre developers live by copy/paste.  Other times features converge and aren’t combined.  Tools for finding similar code are great in the example of copy/paste problems.  Knowledge of the domain helps identify convergent concepts that often lead to convergent solutions and will give intuition for where to look for conceptual repetition. 80/20 and the Boy Scouts It’s often said that 80% of the time 20% of the application is used most.  These tend to be the parts that are changed.  There are also parts of the code where 80% of the time is spent changing 20% (probably for all the refactoring smells above).  I focus on these areas any time I make a change and follow the philosophy of the Boy Scout in cleaning up more than I messed up.  If I spend 2 hours changing an application, in the 20%, I’ll always spend at least 15 minutes cleaning it or nearby areas. This gives a huge productivity edge on developers that don’t. Ironically after a short period of time the 20% shrinks enough that we don’t have to spend 80% of our time there and can move on to other areas.   Refactoring is highly subjective, never attempt to refactor to completion!  Learn to be comfortable with leaving one part of the application in a better state than others.  It’s an evolution, not a revolution.  These are some simple areas to look into when making changes and can help get one started in the process.  I’ve often found that refactoring is a convergent process towards simplicity that sometimes spans a few hours but often can lead to massive simplifications over the timespan of weeks and months of regular development.

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• What would cause different rates of packet loss between client and server in UDP?

  - by febreezey

  If I've implemented a reliable UDP file transfer protocol and I have a file that deliberately drops a percentage of packets when I transmit, why would it be more evident that transmission time increases as the packet loss percentage increases going from the client to server as opposed from the server to the client? Is this something that can be explained as a result of the protocol? Here are my numbers from two separate experiments. I kept the max packet size to 500 Bytes and the opposite direction packet loss to 5% with a 1 Megabyte file: Server to Client loss Percentage varied: 1 MB file, 500 b segments, client to server loss 5% 1% : 17253 ms 3% : 3388 ms 5% : 7252 ms 10% : 6229 ms 11% : 12346 ms 13% : 11282 ms 15% : 9252 ms 20% : 11266 ms Client to Server loss percentage varied 1 MB file, 500 b segments, server to client loss 5% 1%: 4227 ms 3%: 4334 ms 5%: 3308 ms 10%: 31350 ms 11%: 36398 ms 13%: 48436 ms 15%: 65475 ms 20%: 120515 ms You can clearly see an exponential increase in the client to server group

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• How to develop an english .com domain value rating algorithm?

  - by Tom

  I've been thinking about an algorithm that should rougly be able to guess the value of an english .com domain in most cases. For this to work I want to perform tests that consider the strengths and weaknesses of an english .com domain. A simple point based system is what I had in mind, where each domain property can be given a certain weight to factor it's importance in. I had these properties in mind: domain character length Eg. initially 20 points are added. If the domain has 4 or less characters, no points are substracted. For each extra character, one or more points are substracted on an exponential basis (the more characters, the higher the penalty). domain characters Eg. initially 20 points are added. If the domain is only alphabetic, no points are substracted. For each non-alhabetic character, X points are substracted (exponential increase again). domain name words Scans through a big offline english database, including non-formal speech, eg. words like "tweet" should be recognized. Question 1 : where can I get a modern list of english words for use in such application? Are these lists available for free? Are there lists like these with non-formal words? The more words are found per character, the more points are added. So, a domain with a lot of characters will still not get a lot of points. words hype-level I believe this is a tricky one, but this should be the cause to differentiate perfect but boring domains from perfect and interesting domains. For example, the following domain is probably not that valueable: www.peanutgalaxy.com The algorithm should identify that peanuts and galaxies are not very popular topics on the web. This is just an example. On the other side, a domain like www.shopdeals.com should ring a bell to the hype test, as shops and deals are quite popular on the web. My initial thought would be to see how often these keywords are references to on the web, preferably with some database. Question 2: is this logic flawed, or does this hype level test have merit? Question 3: are such "hype databases" available? Or is there anything else that could work offline? The problem with eg. a query to google is that it requires a lot of requests due to the many domains to be tested. domain name spelling mistakes Domains like "freemoneyz.com" etc. are generally (notice I am making a lot of assumptions in this post but that's necessary I believe) not valueable due to the spelling mistakes. Question 4: are there any offline APIs available to check for spelling mistakes, preferably in javascript or some database that I can use interact with myself. Or should a word list help here as well? use of consonants, vowels etc. A domain that is easy to pronounce (eg. Google) is usually much more valueable than one that is not (eg. Gkyld). Question 5: how does one test for such pronuncability? Do you check for consonants, vowels, etc.? What does a valueable domain have? Has there been any work in this field, where should I look? That is what I came up with, which leads me to my final two questions. Question 6: can you think of any more english .com domain strengths or weaknesses? Which? How would you implement these? Question 7: do you believe this idea has any merit or all, or am I too naive? Anything I should know, read or hear about? Suggestions/comments? Thanks!

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• Backing up SQL Azure

  - by Herve Roggero

  That's it!!! After many days and nights... and an amazing set of challenges, I just released the Enzo Backup for SQL Azure BETA product (http://www.bluesyntax.net). Clearly, that was one of the most challenging projects I have done so far. Why??? Because to create a highly redundant system, expecting failures at all times for an operation that could take anywhere from a couple of minutes to a couple of hours, and still making sure that the operation completes at some point was remarkably challenging. Some routines have more error trapping that actual code... Here are a few things I had to take into account: Exponential Backoff (explained in another post) Dual dynamic determination of number of rows to backup  Dynamic reduction of batch rows used to restore the data Implementation of a flexible BULK Insert API that the tool could use Implementation of a custom Storage REST API to handle automatic retries Automatic data chunking based on blob sizes Compression of data Implementation of the Task Parallel Library at multiple levels including deserialization of Azure Table rows and backup/restore operations Full or Partial Restore operations Implementation of a Ghost class to serialize/deserialize data tables And that's just a partial list... I will explain what some of those mean in future blob posts. A lot of the complexities had to do with implementing a form of retry logic, depending on the resource and the operation.

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• Case Study: Polystar Improves Telecom Networks Performance with Embedded MySQL

  - by Bertrand Matthelié

  Polystar delivers and supports systems that increase the quality, revenue and customer satisfaction of telecommunication services. Headquarted in Sweden, Polystar helps operators worldwide including Telia, Tele2, Telekom Malysia and T-Mobile to monitor their network performance and improve service levels. Challenges Deliver complete turnkey solutions to customers integrating a database ensuring high performance at scale, while being very easy to use, manage and optimize. Enable the implementation of distributed architectures including one database per server while maintaining a low Total Cost of Ownership (TCO). Avoid growing database complexity as the volume of mobile data to monitor and analyze drastically increases. Solution Evaluation of several databases and selection of MySQL based on its high performance, manageability, and low TCO. The MySQL databases implemented within the Polystar solutions handle on average 3,000 to 5,000 transactions per second. Up to 50 million records are inserted every day in each database. Typical installations include between 50 and 100 MySQL databases, up to 300 for the largest ones. Data is then periodically aggregated, with the original records being overwritten, as the need for detailed information becomes unnecessary to operators after a few weeks. The exponential growth in mobile data traffic driven by the proliferation of smartphones and usage of social media requires ever more powerful solutions to monitor, analyze and turn network data into actionable business intelligence. With MySQL, Polystar can deliver powerful, yet easy to manage, solutions to its customers. MySQL-based Polystar solutions enable operators to monitor, manage and improve the service levels of their telecom networks in over a dozen countries from a single location. The new and innovative MySQL features constantly delivered by Oracle help ensure Polystar that it will be able to meet its customer’s needs as they evolve. “MySQL has been a great embedded database choice for us. It delivers the high performance we need while remaining very easy to use, manage and tune. Power and simplicity at its best.” Mats Söderlindh, COO at Polystar.

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• best way to compute vertex normals from a Triangle's list

  - by nkint

  hi i'm a complete newbie in computergraphics so sorry if it's a stupid answer. i'm trying to make a simple 3d engine from scratch, more for educational purpose than for real use. i have a Surface object with inside a Triangle's list. For now i compute normals inside Triangle class, in this way: triangle.computeFaceNormals() { Vec3D u = v1.sub(v3) Vec3D v = v1.sub(v2) Vec3D normal = Vec3D.cross(u,v) normal.normalized() this.n1 = this.n2 = this.n3 = normal } and when building surface: t = new Triangle(v1,v2,v3).computeFaceNormals() surface.addTriangle(t) and i think this is the best way to do that.. isn't it? now.. what about for vertex normals? i've found this simple algorithm: flipcode vertex normal but.. hei this algorithm has.. exponential complexity? (if my memory doesn't fail my computer science background..) (bytheway.. it has 3 nested loops.. i don't think it's the best way to do it..) any suggestion?

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• Webcast: Sun2Oracle: Upgrading from DSEE to the next generation Oracle Unified Directory

  - by Etienne Remillon

  Interested in upgrading from DSEE to OUD? Register to learn from one customer. Oracle Security Solutions Sun2Oracle: Upgrading from DSEE to the next generation Oracle Unified Directory Oracle Unified Directory (OUD) is the world’s first unified directory solution with highly integrated storage, synchronization, and proxy capabilities. These capabilities help meet the evolving needs of enterprise architectures. OUD customers can lower the cost of administration and ownership by maintaining a single directory for all of their enterprise needs, while also simplifying their enterprise architecture. OUD is optimized for mobile and cloud computing environments where elastic scalability becomes critical as service providers need a solution that can scale by dynamically adding more directory instances without re-architecting their solutions to support exponential business growth. Join us for this webcast and you will: Learn from one customer that has successfully upgraded to the new platform See what technology and business drivers influenced the upgrade Hear about the benefits of OUD’s elastic scalability and unparalleled performance Get additional information and resources for planning an upgrade Register here for the webcast. REGISTER NOW Register now for this complimentary webcast: Sun2Oracle: Upgrading from DSEE to the next generation Oracle Unified Directory Thursday September 13, 2012 10:00 a.m. PT / 1:00 p.m. ET

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• Algorithm for dynamically calculating a level based on experience points?

  - by George

  One of the struggles I've always had in game development is deciding how to implement experience points attributed to gaining a level. There doesn't seem to be a pattern to gaining a level in many of the games I've played, so I assume they have a static dictionary table which contains experience points vs. the level. e.g. Experience Level 0 1 100 2 175 3 280 4 800 5 ...There isn't a rhyme or reason why 280 points is equal to level 4, it just is. I'm not sure how those levels are decided, but it certainly wouldn't be dynamic. I've also thought about the possibility of exponential levels, as not to have to keep a separate lookup table, e.g. Experience Level 0 1 100 2 200 3 400 4 800 5 1600 6 3200 7 6400 8 ...but that seems like it would grow out of control rather quickly, as towards the upper levels, the enemies in the game would have to provide a whopping amount of experience to level -- and that would be to difficult to control. Leveling would become an impossible task. Does anyone have any pointers, or methods they use to decide how to level a character based on experience? I want to be fair in leveling and I want to stay ahead of the players as not to worry about constantly adding new experience/level lookups.

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• The Simplicity of the Oracle Stack

  - by user801960

  For many retailers, technology is something they know they need to optimise business operations, but do they really understand it and how can they select the solutions they need from the many vendors on the market? Retail is a data heavy industry, with the average retailer managing thousands of SKUs and hundreds of categories through multiple channels. Add to this the exponential growth in data driven by social media and mobile activities, and the process can seem overwhelming. Handling data of this magnitude and analyzing it effectively to gain actionable insight is a huge task, and needs several IT components to work together harmoniously to make the best use of the data available and make smarter decisions. With this in mind, Oracle has produced a video to make it easier for businesses to understand its global data IT solutions and how they integrate seamlessly with Oracle’s other solutions to enable organisations to operate as effectively as possible. The video uses an orchestra as an analogy for IT solutions and clever illustration to demonstrate the value of the Oracle brand. This video can be viewed at http://medianetwork.oracle.com/video/player/1622148401001. To find out more about how Oracle’s products and services can help retailers to deliver better results, visit the Oracle Retail website.

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• Estimate of Hits / Visits / Uniques in order to fall within a given Alexa Tier?

  - by Alex C

  I was wondering if anyone could offer up rough estimates that could tell me how many hits a day move you into a given Alexa rank ? Top 5,000 Top 10,000 Top 50,000 Top 100,000 Top 500,000 Top 1,000,000 I know this is incredibly subjective and thus the broad brush strokes with the number ranges... BUT I've got a site currently ranked just over 1.2M worldwide and over 500k in the USA (http://www.alexa.com/siteinfo/fstr.net) Pretty cool for something hand-built on weekends (pat self on back) I was applying to an ad-platform and was told that their program doesn't accept webmasters who have an Alexa rank of greater than 100,000. (Time to take back that pat on the back I guess). I know that my hits in the last 30 days are somewhere on the order of 15,000 uniques and 20,000 pageviews. So I'm wondering how much harder do I have to work to achieve my next "goals"? I'd like to break into the top million, then re-evaluate from there. It'd be nice to know what those targets translate into (very roughly of course). I imagine that alexa ranks and tiers become very much exponential as you move up the ranks, but even hearing annecdotal evidence from other webmasters would be really useful to me. (ie: I have a site that is ranked X and it got Y hits in the last 30 days) Thanks :) - Alex

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• Estimate of Hits / Visits / Uniques in order to fall within a given Alexa Tier?

  - by Alex C

  Hi there! I was wondering if anyone could offer up rough estimates that could tell me how many hits a day move you into a given Alexa rank ? Top 5,000 Top 10,000 Top 50,000 Top 100,000 Top 500,000 Top 1,000,000 I know this is incredibly subjective and thus the broad brush strokes with the number ranges... BUT I've got a site currently ranked just over 1.2M worldwide and over 500k in the USA (http://www.alexa.com/siteinfo/fstr.net) Pretty cool for something hand-built on weekends (pat self on back) I was applying to an ad-platform and was told that their program doesn't accept webmasters who have an Alexa rank of greater than 100,000. (Time to take back that pat on the back I guess). I know that my hits in the last 30 days are somewhere on the order of 15,000 uniques and 20,000 pageviews. So I'm wondering how much harder do I have to work to achieve my next "goals"? I'd like to break into the top million, then re-evaluate from there. It'd be nice to know what those targets translate into (very roughly of course). I imagine that alexa ranks and tiers become very much exponential as you move up the ranks, but even hearing annecdotal evidence from other webmasters would be really useful to me. (ie: I have a site that is ranked X and it got Y hits in the last 30 days) Thanks :) - Alex

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• How to output floating point numbers with a custom output format in C++?

  - by Victor Liu

  The problem is that I want to output Mathematica compatible floating point numbers. The only difference with the standard IOStream or printf output format is that the exponential e is replaced by *^: Standard C/C++ output format: 1.23e-4 Mathematica format: 1.23*^-4 Is there a way to manipulate streams to achieve this effect? My original idea was just to use istringstream and dump it to a string and then replace all the e's. I would also be okay if someone posted code to parse through the bits of the floating point number and output it directly (i.e. a printf("%e") replacement).

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• Why does tokyo tyrant slow down exponentially even after adjusting bnum?

  - by HenryL

  Has anyone successfully used Tokyo Cabinet / Tokyo Tyrant with large datasets? I am trying to upload a subgraph of the Wikipedia datasource. After hitting about 30 million records, I get exponential slow down. This occurs with both the HDB and BDB databases. I adjusted bnum to 2-4x the expected number of records for the HDB case with only a slight speed up. I also set xmsiz to 1GB or so but ultimately I still hit a wall. It seems that Tokyo Tyrant is basically an in memory database and after you exceed the xmsiz or your RAM, you get a barely usable database. Has anyone else encountered this problem before? Were you able to solve it?

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• Check if a string substitution rule will ever generate another string.

  - by Mgccl

  Given two strings S and T of same length. Given a set of replacement rules, that find substring A in S and replace it with string B. A and B have the same length. Is there a sequence of rule application, such that it make string S into string T? I believe there is no better way to answer this than try every single rule in every single state. Which would be exponential time. But I don't know if there are better solutions to it.

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• Would it be simply better to use the system's functions rather than use the language?

  - by Nullw0rm

  There are many scenarios where I've questioned PHP's performance with some of its functions, and whether I should build a complex class to handle specific things using its seemingly slow tools. For example, Complex regular expressions with sed and processing with awk would seemingly be exponential in performance rather than making PHP's regular expression and seemingly excessive functions parse and in time manage to finish it. If I were to do a lot of network tasks such as MX lookups/DIGging/retrieving simultaneously I would rather pass it via system() and let the OS handle it itself. There are simply too many functions in PHP, that are inefficient and result in slow pages or can be handled easier by the OS. What are your opinions? Do you think I should do the hard work with the OS in its own/custom functions?

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• "Winamp style" spectrum analyzer

  - by cvb

  I have a program that plots the spectrum analysis (Amp/Freq) of a signal, which is preety much the DFT converted to polar. However, this is not exactly the sort of graph that, say, winamp (right at the top-left corner), or effectively any other audio software plots. I am not really sure what is this sort of graph called (if it has a distinct name at all), so I am not sure what to look for. I am preety positive about the frequency axis being base two exponential, the amplitude axis puzzles me though. Any pointers?

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• R: Given a set of random numbers drawn from a continuous univariate distribution, find the distribut

  - by knorv

  Given a set of real numbers drawn from a unknown continuous univariate distribution (let's say is is one of beta, Cauchy, chi-square, exponential, F, gamma, Laplace, log-normal, normal, Pareto, Student's t, uniform and Weibull).. x <- c(15.771062,14.741310,9.081269,11.276436,11.534672,17.980860,13.550017,13.853336,11.262280,11.049087,14.752701,4.481159,11.680758,11.451909,10.001488,11.106817,7.999088,10.591574,8.141551,12.401899,11.215275,13.358770,8.388508,11.875838,3.137448,8.675275,17.381322,12.362328,10.987731,7.600881,14.360674,5.443649,16.024247,11.247233,9.549301,9.709091,13.642511,10.892652,11.760685,11.717966,11.373979,10.543105,10.230631,9.918293,10.565087,8.891209,10.021141,9.152660,10.384917,8.739189,5.554605,8.575793,12.016232,10.862214,4.938752,14.046626,5.279255,11.907347,8.621476,7.933702,10.799049,8.567466,9.914821,7.483575,11.098477,8.033768,10.954300,8.031797,14.288100,9.813787,5.883826,7.829455,9.462013,9.176897,10.153627,4.922607,6.818439,9.480758,8.166601,12.017158,13.279630,14.464876,13.319124,12.331335,3.194438,9.866487,11.337083,8.958164,8.241395,4.289313,5.508243,4.737891,7.577698,9.626720,16.558392,10.309173,11.740863,8.761573,7.099866,10.032640) .. is there some easy way in R to programmatically and automatically find the most likely distribution and the estimated distribution parameters?

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