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  • Aggregating, restructuring hourly time series data in R

    - by Advait Godbole
    I have a year's worth of hourly data in a data frame in R: > str(df.MHwind_load) # compactly displays structure of data frame 'data.frame': 8760 obs. of 6 variables: $ Date : Factor w/ 365 levels "2010-04-01","2010-04-02",..: 1 1 1 1 1 1 1 1 1 1 ... $ Time..HRs. : int 1 2 3 4 5 6 7 8 9 10 ... $ Hour.of.Year : int 1 2 3 4 5 6 7 8 9 10 ... $ Wind.MW : int 375 492 483 476 486 512 421 396 456 453 ... $ MSEDCL.Demand: int 13293 13140 12806 12891 13113 13802 14186 14104 14117 14462 ... $ Net.Load : int 12918 12648 12323 12415 12627 13290 13765 13708 13661 14009 ... While preserving the hourly structure, I would like to know how to extract a particular month/group of months the first day/first week etc of each month all mondays, all tuesdays etc of the year I have tried using "cut" without result and after looking online think that "lubridate" might be able to do so but haven't found suitable examples. I'd greatly appreciate help on this issue.

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  • Database entries existence depends on time / boolean value of a field changed automatically

    - by lisak
    Hey, I have this situation here. An auction system listing orders that are "active" (their deadline didn't occur yet) There is a lot of orders so it is better to have a field "active" instead of listing them based on time queries I'm not a database expert, just a user. What is the best way to implement this scenario ? Do I have to manually check the "deadLine" field and change "active" status every once in a while ? Is Mysql able to change the field automatically ? How demanding are queries of type "select orders where "deadline" has passed " Do I need to use TIMESTAMP (long data type of number of milisecond since UTC epoch time or DATETIME for the queries to the database to be more efficient ? Finally I have to move old order entries to a different backup table .

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  • Using Moq at Blend design time

    - by adrian hara
    This might be a bit out there, but suppose I want to use Moq in a ViewModel to create some design time data, like so: public class SomeViewModel { public SomeViewModel(ISomeDependency dependency) { if (IsInDesignMode) { var mock = new Mock<ISomeDependency>(); dependency = mock.Object; // this throws! } } } The mock could be set up to do some stuff, but you get the idea. My problem is that at design-time in Blend, this code throws an InvalidCastException, with the message along the lines of "Unable to cast object of type 'Castle.Proxies.ISomeDependencyProxy2b3a8f3188284ff0b1129bdf3d50d3fc' to type 'ISomeDependency'." While this doesn't necessarily look to be Moq related but Castle related, I hope the Moq example helps ;) Any idea why that is? Thanks!

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  • What is considered a long execution time?

    - by stjowa
    I am trying to figure out just how "efficient" my server-side code is. Using start and end microtime(true) values, I am able to calculate the time it took my script to run. I am getting times from .3 - .5 seconds. These scripts do a number of database queries to return different values to the user. What is considered an efficient execution time for PHP scripts that will be run online for a website? Note: I know it depends on exactly what is being done, but just consider this a standard script that reads from a database and returns values to the user. Also, I look at Google and see them search the internet in .15 seconds and I feel like my script is crap. Thanks.

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  • select time (HH:MM:SS.mmm) in javascript

    - by acidzombie24
    I would like the user to select the time in javascript and to avoid selecting the wrong time. How should i do it? Is there some kind of javascript or jquery widget? or should i show the format and allow users to write it in (and i guess check it with regex)? i think these should be valid 1 (1s) 1:5 (1m 5s) 1.5 (1s, 500 milliseconds. not to be confused by the above) 1:2:02 (1h, 2m, 2 seconds) 1:2:2 (1h, 2m, 2 seconds) 1:2:20 (1h, 2m, 20 seconds) I dont want the user to be confused. How can i avoid this?

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  • What is the best server side solution for a real-time GPS tracking system

    - by Ayman
    Well, I tried to ask this question as a comment on this question, but I thought that maybe no one will notice it, so I decided to ask it as a separate one. The question is about how to do real-time GPS tracking system things; if we have the following scenario: Rather than connecting a GPS receiver to a PC, the user will have a mobile device with an integrated GPS receiver. Location data will be sent over mobile network using GPRS data connection to a server side. The data will be processed and a KML path file will be created and updated on time intervals and used to track the user using Google Earth. The question is: what is the best method to accomplish this scenario for the server side; is it a web service, a web application, a windows service, a windows application or what exactly? Taking into account that the system will serve a number of users simultaneously, and that more users may use the system in the future(scalability issues). Thank you in advance and I highly appreciate any help :)

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  • difficulty based time estimation software

    - by Frankie
    Some months ago I found a project-management / time-estimation software that would ask you to sort out your tasks in terms of difficulty (1, 2 or 3) and would then estimate the time you would take to deploy. The system would auto-adapt as you were working. I've forgot the software name. For the past days I've been digging emails and searching Google with no results. Can anyone pin the software name by my description? Its not http://www.fogcreek.com (though I've found it to be a great piece of software. Thank you in advance.

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  • Haskell compile time function calculation

    - by egon
    I would like to precalculate values for a function at compile-time. Example (real function is more complex, didn't try compiling): base = 10 mymodulus n = n `mod` base -- or substitute with a function that takes -- too much to compute at runtime printmodules 0 = [mymodulus 0] printmodules z = (mymodulus z):(printmodules (z-1)) main = printmodules 64 I know that mymodulus n will be called only with n < 64 and I would like to precalculate mymodulus for n values of 0..64 at compile time. The reason is that mymodulus would be really expensive and will be reused multiple times.

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  • c++ quick sort running time

    - by chnet
    I have a question about quick sort algorithm. I implement quick sort algorithm and play it. The elements in initial unsorted array are random numbers chosen from certain range. I find the range of random number effects the running time. For example, the running time for 1, 000, 000 random number chosen from the range (1 - 2000) takes 40 seconds. While it takes 9 seconds if the 1,000,000 number chosen from the range (1 - 10,000). But I do not know how to explain it. In class, we talk about the pivot value can effect the depth of recursion tree. For my implementation, the last value of the array is chosen as pivot value. I do not use randomized scheme to select pivot value. int partition( vector<int> &vec, int p, int r) { int x = vec[r]; int i = (p-1); int j = p; while(1) { if (vec[j] <= x){ i = (i+1); int temp = vec[j]; vec[j] = vec[i]; vec[i] = temp; } j=j+1; if (j==r) break; } int temp = vec[i+1]; vec[i+1] = vec[r]; vec[r] = temp; return i+1; } void quicksort ( vector<int> &vec, int p, int r) { if (p<r){ int q = partition(vec, p, r); quicksort(vec, p, q-1); quicksort(vec, q+1, r); } } void random_generator(int num, int * array) { srand((unsigned)time(0)); int random_integer; for(int index=0; index< num; index++){ random_integer = (rand()%10000)+1; *(array+index) = random_integer; } } int main() { int array_size = 1000000; int input_array[array_size]; random_generator(array_size, input_array); vector<int> vec(input_array, input_array+array_size); clock_t t1, t2; t1 = clock(); quicksort(vec, 0, (array_size - 1)); // call quick sort int length = vec.size(); t2 = clock(); float diff = ((float)t2 - (float)t1); cout << diff << endl; cout << diff/CLOCKS_PER_SEC <<endl; }

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  • How to get current date and time from DB using SQLAlchemy

    - by bluish
    I need to retrieve what's the current date and time for the database I'm connected with SQLAlchemy (not date and time of the machine where I'm running Python code). I've seen this functions, but they don't seem to do what they say: >>> from sqlalchemy import * >>> print func.current_date() CURRENT_DATE >>> print func.current_timestamp() CURRENT_TIMESTAMP Moreover it seems they don't need to be binded to any SQLAlchemy session or engine. It makes no sense... Thanks!

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  • Group MySQL Data into Arbitrarily Sized Time Buckets

    - by Eric J.
    How do I count the number of records in a MySQL table based on a timestamp column per unit of time where the unit of time is arbitrary? Specifically, I want to count how many record's timestamps fell into 15 minute buckets during a given interval. I understand how to do this in buckets of 1 second, 1 minute, 1 hour, 1 day etc. using MySQL date functions, e.g. SELECT YEAR(datefield) Y, MONTH(datefield) M, DAY(datefield) D, COUNT(*) Cnt FROM mytable GROUP BY YEAR(datefield), MONTH(datefield), DAY(datefield) but how can I group by 15 minute buckets?

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  • Store time of the day in SQL

    - by nute
    How would you store a time or time range in SQL? It won't be a datetime because it will just be let's say 4:30PM (not, January 3rd, 4:30pm). Those would be weekly, or daily meetings. The type of queries that I need are of course be for display, but also later will include complex queries such as avoiding conflicts in schedule. I'd rather pick the best datatype for that now. I'm using MS SQL Server Express 2005. Thanks! Nathan

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  • Time complexity O() of isPalindrome()

    - by Aran
    I have this method, isPalindrome(), and I am trying to find the time complexity of it, and also rewrite the code more efficiently. boolean isPalindrome(String s) { boolean bP = true; for(int i=0; i<s.length(); i++) { if(s.charAt(i) != s.charAt(s.length()-i-1)) { bP = false; } } return bP; } Now I know this code checks the string's characters to see whether it is the same as the one before it and if it is then it doesn't change bP. And I think I know that the operations are s.length(), s.charAt(i) and s.charAt(s.length()-i-!)). Making the time-complexity O(N + 3), I think? This correct, if not what is it and how is that figured out. Also to make this more efficient, would it be good to store the character in temporary strings?

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  • User control attributes at design-time

    - by ciscoheat
    I'm testing a simple User Control in Visual Studio 2008: A Panel named Wrapper with some controls inside. Can Visual Studio handle this at design time? public partial class TestControl : System.Web.UI.UserControl { [Description("Css class of the div around the control.")] [CssClassProperty] public string CssClass { get { return Wrapper.CssClass; } set { Wrapper.CssClass = value; } } } When setting the CssClass property, it doesn't update the css of the Panel at design time. Am I hoping for too much?

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  • Time Complexities of recursive algorithms

    - by Peter
    Whenever I see a recursive solution, or I write recursive code for a problem, it is really difficult for me to figure out the time complexity, in most of the cases I just say its exponential? How is it exponential actually? How people say it is 2^n, when it is n!, when it is n^n or n^k. I have some questions in mind, let say find all permutations of a string (O(n!)) find all sequences which sum up to k in an array (exponential, how exactly do I calculate). Find all subsets of size k whose sum is 0 (will k come somewhere in complexity , it should come right?). Can any1 help me how to calculate the exact complexity of such questions, I am able to wrote code for them , but its hard understanding the exact time complexity.

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  • MySQL Split Time Ranges into Smaller Chunks

    - by Neren
    Hello all, I've recently been tasked with finishing a PHP/MySQL web app when the developer quit last week. I'm no MySQL expert, so I apologize if this is an intensely simple question. I've searched SO for the better part of two days trying to find a relatively easy solution to my problem, which is as follows. Problem in a Nutshell: I have a MySQL table full of start and end datetime (GMT -5) & UNIX Timestamp values covering durations of irregular length and need to break/split/divide them into more-regular time chunks (5 minutes). I'm not after a count of row entries per time chunk/bucket/period, if that makes any sense. Data Example: started, ended, started_UNIX, ended_UNIX 2010-10-25 15:12:33, 2010-10-25 15:47:09, 1288033953, 1288036029 What I'm hoping to get: 2010-10-25 15:12:33, 2010-10-25 15:15:00, 1288033953, 1288037700 2010-10-25 15:15:00, 2010-10-25 15:20:00, 1288037700, 1288038000 2010-10-25 15:20:00, 2010-10-25 15:25:00, 1288038000, 1288038300 2010-10-25 15:25:00, 2010-10-25 15:30:00, 1288038300, 1288038600 2010-10-25 15:30:00, 2010-10-25 15:35:00, 1288038600, 1288038900 2010-10-25 15:35:00, 2010-10-25 15:40:00, 1288038900, 1288039200 2010-10-25 15:40:00, 2010-10-25 15:45:00, 1288039200, 1288039500 2010-10-25 15:45:00, 2010-10-25 15:47:09, 1288039500, 1288039629 If you're interested, here's the quick & dirty on the app and why I need the data: App overview: The application receives very simple POST requests generated by a basic sensor device when its input pins go to ground, which submits an INSERT query to the database where MySQL records a timestamp (as started). When the input pins return from a grounded state, the device submits a different POST request, which causes the PHP app to submit an UPDATE query, where a modification time timestamp is inserted (as ended). My employer recently changed the periodic reporting unit of measure from Seconds "On" Per Day to Seconds "On" Per 5 Minute Interval. I had formulated what I thought would be a workable solution, but when I looked at it on paper, it looked like Rube Goldberg's nightmare constructed in MySQL, so that was out. Any suggestions as to how to break these spans into 5 minute blocks? Keeping it all in MySQL would be my preference, though I'll take any suggestions. Thank you for any suggestions you may have. Again, I apologize if this is a no-brainer. If I ask any additional questions of the SO collective consciousness in the future, I'll try to word them a bit better. Any help will be happily welcomed. Thanks, Neren

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  • Rails: How do I get created_at to show the time in my current time zone?

    - by Schneems
    Seems that when i create an object, the time is not correct. You can see by the script/console output below. Has anyone encountered anything like this, or have any debugging tips? >> Ticket.create(...) => #<Ticket id: 7, from_email: "[email protected]", ticket_collaterals: nil, to_email: "[email protected]", body: "hello", subject: "testing", status: nil, whymail_id: nil, created_at: "2009-12-31 04:23:20", updated_at: "2009-12-31 04:23:20", forms_id: nil, body_hash: nil> >> Ticket.last.created_at.to_s(:long) => "December 31, 2009 04:23" >> Time.now.to_s(:long) => "December 30, 2009 22:24"

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  • c++ thread running time

    - by chnet
    I want to know whether I can calculate the running time for each thread. I implement a multithread program in C++ using pthread. As we know, each thread will compete the CPU. Can I use clock() function to calculate the actual number of CPU clocks each thread consumes? my program looks like: Class Thread () { Start(); Run(); Computing(); }; Start() is to start multiple threads. Then each thread will run Computing function to do something. My question is how I can calculate the running time of each thread for Computing function

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  • Using system time directly to get random numbers

    - by Richard Mar.
    I had to return a random element from an array so I came up with this placeholder: return codes[(int) (System.currentTimeMillis() % codes.length - 1)]; Now than I think of it, I'm tempted to use it in real code. The Random() seeder uses system time as seed in most languages anyway, so why not use that time directly? As a bonus, I'm free from the worry of non-random lower bits of many RNGs. It this hack coming back to bite me? (The language is Java if that's relevant.)

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