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  • reservoir sampling problem

    - by eSKay
    This MSDN article proves the correctness of Reservoir Sampling algorithm as follows: Base case is trivial. For the k+1st case, the probability a given element i with position <= k is in R is s/k. The probability i is replaced is the probability k+1st element is chosen multiplied by i being chosen to be replaced, which is: s/(k+1) * 1/s = 1/(k+1), and prob that i is not replaced is k/k+1. So any given element's probability of lasting after k+1 rounds is: (chosen in k steps, and not removed in k steps) = s/k * k/(k+1), which is s/(k+1). So, when k+1 = n, any element is present with probability s/n. about step 3: What are the k+1 rounds mentioned? What is chosen in k steps, and not removed in k steps? Why are we only calculating this probability for elements that were already in R after the first s steps?

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  • Biased Random Number Generator

    - by cmptrer
    I am looking for a random number generator that can be biased. For instance, say I want a random number between 1-5, with the probability being: 1: Comes up 20% of the time 2: Comes up 10% of the time 3: Comes up 40% of the time 4: Comes up 25% of the time 5: Comes up 5% of the time Is there anything in the standard library, or other libraries out there that would do this? Alternatively, is there an efficient way to do this myself?

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  • Using regex to fix phone numbers in a CSV with PHP

    - by Hurpe
    My new phone does not recognize a phone number unless it's area code matches the incoming call. Since I live in Idaho where an area code is not needed for in-state calls, many of my contacts were saved without an area code. Since I have thousands of contacts stored in my phone, it would not be practical to manually update them. I decided to write the following PHP script to handle the problem. It seems to work well, except that I'm finding duplicate area codes at the beginning of random contacts. <?php //the script can take a while to complete set_time_limit(200); function validate_area_code($number) { //digits are taken one by one out of $number, and insert in to $numString $numString = ""; for ($i = 0; $i < strlen($number); $i++) { $curr = substr($number,$i,1); //only copy from $number to $numString when the character is numeric if (is_numeric($curr)) { $numString = $numString . $curr; } } //add area code "208" to the beginning of any phone number of length 7 if (strlen($numString) == 7) { return "208" . $numString; //remove country code (none of the contacts are outside the U.S.) } else if (strlen($numString) == 11) { return preg_replace("/^1/","",$numString); } else { return $numString; } } //matches any phone number in the csv $pattern = "/((1? ?\(?[2-9]\d\d\)? *)? ?\d\d\d-?\d\d\d\d)/"; $csv = file_get_contents("contacts2.CSV"); preg_match_all($pattern,$csv,$matches); foreach ($matches[0] as $key1 => $value) { /*create a pattern that matches the specific phone number by adding slashes before possible special characters*/ $pattern = preg_replace("/\(|\)|\-/","\\\\$0",$value); //create the replacement phone number $replacement = validate_area_code($value); //add delimeters $pattern = "/" . $pattern . "/"; $csv = preg_replace($pattern,$replacement,$csv); } echo $csv; ?> Is there a better approach to modifying the csv? Also, is there a way to minimize the number of passes over the csv? In the script above, preg_replace is called thousands of times on a very large String.

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  • howto use JFormattedTextField allowing only letters and numbers

    - by Erik
    I have this code and cannot get MaskFormatter right maskformatter MaskFormatter formatter = null; try { formatter = new MaskFormatter("HHHHHHH"); } catch (ParseException e) { e.printStackTrace(); } txtTroll = new JFormattedTextField(formatter); I need Any hex character (0-9, a-f or A-F) and the "H" should give me only (0-9, a-f or A-F) but im getting it wrong. When i type text only capital letters are typed and it's slow to and when i click away from the txtTroll all letters vanish

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  • Jquery flot and week numbers

    - by mark
    I've plotted some nice graphs with jquery flot. On the x-as the weeknumber is displayed. I would like to display the weeknumbers of the winter season (oct-apr) but that is not possible 'cos flot likes a straight set (0,1,2,3,4 etc) and not (49, 50, 51, 52, 1, 2 etc). Does anyone know how to fix it? http://sionvalais.com/snowcondition/andermatt/36

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  • HttpContext.Current.Request.Url.Host returns a string of numbers

    - by Jonathan Sewell
    I have a website that emails a link to the invoice when an order is complete. The link should be http://mysite.com/QuoteAndBook/Confirmation?orderId=123 But for some reason it is: http://204435-204435/QuoteAndBook/Confirmation?orderId=123 The host portion of the link is generated using HttpContext.Current.Request.Url.Host but I would expect that to return "mysite.com", not "204435-204435". Any idea what's going on?

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  • Regex for tollfree numbers in java

    - by arinte
    I have this regex to test for telephone # that should be a toll free. public static final Pattern patternTollFree = Pattern.compile("^((877)|(800)|(866)|(888))"); So I only want to get those # where the user may have left the 1 off of the front of the string, but I have tried several things and I can't get java to match. public String changeRingTo( String changedRinger ) { if ( null == changedRinger || changedRinger.length() != 10) return changedRinger; if ( patternTollFree.matcher(changedRinger).region(0, 2).matches() ) changedRinger = '1' + changedRinger; return changedRinger; } I can't get this 2nd test case below to succeed. What am I doing wrong? assertEquals( "Regex not working", "8189091000", of.changeRingTo("8189091000")); assertEquals( "Regex not working", "18769091000", of.changeRingTo("8769091000"));

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  • Why does does my stack overflow error occur after 518669 specifically?

    - by David
    I created a java program to count up toward infinity: class up { public static void up (int n) { System.out.println (n) ; up (n+1) ; } public static void main (String[] arg) { up (1) ; } } i didn't actually expect it to get there but the thing that i noticed that was a bit curious was that it stopped at the same number each time: 518669 what is the significance of this number? (or of this number +1 i suppose). (also as a bit of an aside question, I've been told that the way i format my code is bad [indentation and such] what am i doing that isn't desirable?)

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  • how IEEE-754 floating point numbers work

    - by hatorade
    Let's say I have this: float i = 1.5 in binary, this float is represented as: 0 01111111 10000000000000000000000 I broke up the binary to represent the 'signed', 'exponent' and 'fraction' chunks. What I don't understand is how this represents 1.5. The exponent is 0 once you subtract the bias (127 - 127), and the fraction part with the implicit leading one is 1.1. How does 1.1 scaled by nothing = 1.5???

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  • Division, Remainders and only Real Numbers Allowed

    - by Senica Gonzalez
    Trying to figure out this pseudo code. The following is assumed.... I can only use unsigned and signed integers (or long). Division returns a real number with no remainder. MOD returns a real number. Fractions and decimals are not handled. INT I = 41828; INT C = 15; INT D = 0; D = (I / 65535) * C; How would you handle a fraction (or decimal value) in this situation? Is there a way to use negative value to represent the remainder? In this example I/65535 should be 0.638, however, with the limitations, I get 0 with a MOD of 638. How can I then multiply by C to get the correct answer? Hope that makes sense.

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  • JMS Session pooling for large numbers of Topic subscribers

    - by matthewKizoom
    I'm writing an app that will create lots of JMS topic subscribers. What is best practise regarding reusing sessions? A session per subscriber? A pool of sessions? With a session per subscriber the thread count seems unreasonable. Is this a job for something like a ServerSessionPool? What I've seen so far seems to suggest that ServerSessionPool is more geared towards one receiver consuming messages concurrently rather than lots of receivers. I'm currently working with HornetQ 2.0.0GA embedded in JBoss 4.3.0CP6.

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  • Decimal numbers works in iPhone simulator but NOT on iPhone device

    - by matsoftware
    Hi everybody, I noticed a weird behaviour of iPhone OS when using decimal values. The simulator parse them from strings in a correct way but when I test the app on my iPhone it lose the decimal part. In particular, I store values in a dictionary that I retrieve in this way: Code: NSString *thickStr = [dictionary valueForKey:@"thickness"]; NSNumber *thickNum = [[[self class] numberFormatter] numberFromString:thickStr]; [self setSpessore:thickNum]; where the "numberFormatter" class is defined as below: Code: + (NSNumberFormatter *)numberFormatter { static NSNumberFormatter *_formatter; if (_formatter == nil) { _formatter = [[NSNumberFormatter alloc] init]; [_formatter setNumberStyle:NSNumberFormatterDecimalStyle]; [_formatter setFormatterBehavior:NSNumberFormatterBehavior10_4]; [_formatter setGeneratesDecimalNumbers:TRUE]; } return _formatter; } But it doesn't work! The App on iPhone keeps on convert the string to a simple integer, forgetting the decimal part, while the app on iPhone simulator works fine!

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  • How to disable Excel's auto recognition of numbers and text

    - by Yin Zhu
    I used Python to generate a CSV file. But when I open it in Excel, Excel will auto recognize a string into a number if it could be converted. e.g.33E105, which is actually an ID, not a number. How to disable this in Excel while opening a CSV file? Or I need to resort to a excel-python library to output a excel file and specify the format myself? Thanks!

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  • range of line numbers in if condition C programming

    - by nour
    Hello, I'm working on a simple C prorgam, and i'ms tuck with an if test: int line_number = 0; if ((line_number >= argv[2]) && (line_number <= argv[4]) ) gcc says: cp.c:25: warning: comparison between pointer and integer cp.c:25: warning: comparison between pointer and integer What can I do to properly write the range of line I want to deal with ? Thank you!

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  • Convert scientific notation to decimal notation

    - by Ankur
    There is a similar question on SO which suggests using NumberFormat which is what I have done. I am using the parse() method of NumberFormat. public static void main(String[] args) throws ParseException{ DecToTime dtt = new DecToTime(); dtt.decToTime("1.930000000000E+02"); } public void decToTime(String angle) throws ParseException{ DecimalFormat dform = new DecimalFormat(); //ParsePosition pp = new ParsePosition(13); Number angleAsNumber = dform.parse(angle); System.out.println(angleAsNumber); } The result I get is 1.93 I didn't really expect this to work because 1.930000000000E+02 is a pretty unusual looking number, do I have to do some string parsing first to remove the zeros? Or is there a quick and elegant way?

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  • converting numbers to different barcodes

    - by Sten
    i have a .txt file that holds a number of various number inside in a list e.g 0000 1111 2222 3333 4444 i am going a package called libdmtx to convert this to barcodes except i can only create one barcode at a time but instead i want to create 5. Can anyone advise me? Thanks

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  • Convert a string of numbers to a NSTimeInterval

    - by culov
    I know I must be over-complicating this because it NSTimeInterval is just a double, but I just can't seem to get this done properly since I have had very little exposure to objective c. the scenario is as follows: The data im pulling into the app contains two values, startTime and endTime, which are the epoch times in milliseconds. The variables that I want to hold these values are NSTimeInterval *start; NSTimeInterval *end; I decided to store them as NSTimeIntervals but im thinking that maybe i ought to store them as doubles because theres no need for NSTimeIntervals since comparisons can just be done with a primitive. Either way, I'd like to know what I'm missing in the following step, where I try to convert from string to NSTimeInterval: tempString = [truckArray objectAtIndex:2]; tempDouble = [tempString doubleValue]; Now it's safely stored as a double, but I can't get the value into an NSTimeInterval. How should this be accomplished? Thanks

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  • Working with ieee format numbers in ARM

    - by Jake Sellers
    I'm trying to write an ARM program that will convert an ieee number to a TNS format number. TNS is a format used by some super computers, and is similar to ieee but different. I'm trying to use several masks to place the three different "part" of the ieee number in separate registers so I can move them around accordingly. Here is my unpack subroutine: UnpackIEEE LDR r1, SMASK ;load the sign bit mask into r1 LDR r2, EMASK ;load the exponent mask into r2 LDR r3, GMASK ;load the significand mask into r3 AND r4, r0, r1 ;apply sign mask to IEEE and save into r4 AND r5, r0, r2 ;apply exponent mask to IEEE and save into r5 AND r6, r0, r3 ;apply significand mask to IEEE and save into r6 MOV pc, r14 ;return And here are the masks and number declarations so you can understand: IEEE DCD 0x40300000 ;2.75 decimal or 01000000001100000000000000000000 binary SMASK DCD 0x80000000 ;Sign bit mask EMASK DCD 0x7F800000 ;Exponent mask GMASK DCD 0x007FFFFF ;Significand mask When I step through with the debugger, the results I get are not what I expect after working through it on paper. EDIT: What I mean, is that after the subroutine runs, registers 4, 5, and 6 all remain 0. I can't figure out why the masks are not working. I think I do not fully understand how the number is being stored in the register or using the masks wrong. Any help appreciated. If you need more info just ask. EDIT: entry point: Very simple, just trying to get these subroutines working. ENTRY LDR r1, IEEE ;load IEEE num into r1 BL UnpackIEEE ;call unpack sub SWI SWI_Exit ;finish

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  • PHP crc32() only numbers

    - by B11002
    I have a MD5 hash: 10f86782177490f2ac970b8dc4c51014 http://www.fileformat.info/tool/hash.htm?text=10f86782177490f2ac970b8dc4c51014 Result: c74e16d9 but PHP: crc32('10f86782177490f2ac970b8dc4c51014'); Result: -951183655 I don't understand!

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  • RegEx, Php, Preg_match, Phone numbers, Oh my!

    - by Kirk
    How do I find phone number of the following format and store them to a variable. It needs to match 3334445555, 333.444.5555, 333-444-5555, 333 444 5555, (333) 444 5555 and all combinations thereof. Here is the frame of it $regex = expression; if (preg_match ('/$regex/', matches)) { $phone = matches[1]; }

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  • Getting consecutive version numbers from Hibernate's @Version usage once per transaction

    - by Cheradenine
    We use Hibernate with the following version definition for optimistic locking et. al: <version name="version" access="field" column="VERSION" type="long" unsaved-value="negative"/> This is fine and dandy; however, there is one small problem, which is that the first version for some entities is '0', and for others, it is '1'. Why this is happening, is that for some object graphs, an entity will be subject to both onSave and flushDirty - this is reasonable, such as if two object are circular dependencies. However, the version number gets incremented on both occasions, leading to the above '0' / '1' discrepancy. I'd really like the version number only to ever increment once per transaction. However, I can't see a simple way to do this in the hibernate versioning implementation, without hacking about with an Interceptor (which was how I generated a column value for version before, but I wanted hibernate to do it itself)..

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