Search Results

Search found 2773 results on 111 pages for 'calculate'.

Page 72/111 | < Previous Page | 68 69 70 71 72 73 74 75 76 77 78 79  | Next Page >

• MySQL indexes: how do they work?

  - by bob-the-destroyer

  I'm a complete newbie with MySQL indexes. I have several MyISAM tables on MySQL 5.0x having utf8 charsets and collations with 100k+ records each. The primary keys are generally integer. Many columns on each table may have duplicate values. I need to quickly count, sum, average, or otherwise perform custom calculations on any number of fields in each table or joined on any number of others. I found this page giving an overview of MySQL index usage: http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html, but I'm still not sure I'm using indexes right. Just when I think I've made the perfect index out of a collection of fields I want to calculate against, I get the "index must be under 1000 bytes" error. Can anyone explain how to most efficiently create and use indexes to speed up queries? Caveat: upgrading Mysql is not possible in this case. Using Navicat Light for db administration, but this app isn't required.

  Read the article

• Recursive function causing a stack overflow

  - by dbyrne

  I am trying to write a simple sieve function to calculate prime numbers in clojure. I've seen this question about writing an efficient sieve function, but I am not to that point yet. Right now I am just trying to write a very simple (and slow) sieve. Here is what I have come up with: (defn sieve [potentials primes] (if-let [p (first potentials)] (recur (filter #(not= (mod % p) 0) potentials) (conj primes p)) primes)) For small ranges it works fine, but causes a stack overflow for large ranges: user=> (sieve (range 2 30) []) [2 3 5 7 11 13 17 19 23 29] user=> (sieve (range 2 15000) []) java.lang.StackOverflowError (NO_SOURCE_FILE:0) I thought that by using recur this would be a non-stack-consuming looping construct? What am I missing?

  Read the article

• Matlab code help. Backward Euler method.

  - by m0s

  Here is the matlab/freemat code I got to solve ODE numerically using backward Euler method. However the results are inconsistent with my textbook results, and sometimes even ridiculously inconsistent. Please point out what is wrong with the code. I have already asked this question on mathoverflow.com no help there, hope someone here can help. function [x,y]=backEuler(f,xinit,yinit,xfinal,h) %f - this is your y prime %xinit - initial X %yinit - initial Y %xfinal - final X %h - step size n=(xfinal-xinit)/h; %Calculate steps %Inititialize arrays... %1st elements take xinit and yinit corespondigly, the rest fill with 0s x=[xinit zeros(1,n)]; y=[yinit zeros(1,n)]; %Numeric routine for i=1:n x(i+1)=x(i)+h; ynew=y(i)+h*(f(x(i),y(i))); y(i+1)=y(i)+h*f(x(i+1),ynew); end end

  Read the article

• rewrite URLs in CSS files

  - by Don

  Hi, I'm writing a Maven plugin that merges CSS files together. So all the CSS files that match /foo/bar/*.css might get merged to /foo/merged.css. A concern is that in a file such as /foo/bar/baz.css there might be a property such as: background: url("images/pic.jpg") So when the file is merged into /foo/merged.css this will need to be changed to background: url("bar/images/pic.jpg") The recalculated URL obviously depends on 3 factors: original URL original CSS file location merged CSS file location Assuming that the original and merged CSS files are both on the same filesystem, is there a general formula (or Java library) that can be used to calculate the new url given these 3 inputs? Thanks, Don

  Read the article

• Learning Algorithms and Data Structures Fundamentals

  - by valya

  Can you recommend me a book or (better!) a site with many hard problems and exercises about data structures? I'm already answering project Euler questions, but these questions are about interesting, but uncommon algorithms. I hardly used even a simple tree. Maybe there is a site with exercises like: hey, you need to calculate this: ... . Do it using a tree. Now do it using a zipper. Upload your C (Haskell, Lisp, even Pascal or Fortress go) solution. Oh, your solution is so slow! Self-education is very hard then you trying to learn very common, fundamental things. How can I help myself with them without attending to courses or whatever?

  Read the article

• Perl Math::Business::EMA help

  - by Dustin

  Script pulls data from mysql: $DBI::result = $db->prepare(qq{ SELECT close FROM $table WHERE day <= '$DATE' ORDER BY day DESC LIMIT $EMA }); $DBI::result->execute(); while($row = $DBI::result->fetchrow) { print "$row\n"; }; with the following example results: 1.560 1.560 1.550... But I need to work out the EMA using Math::Business::EMA; and I'm not sure how to calculate this while maintaining the accuracy. EMA is weighted and My lack of Perl knowledge is not helping.

  Read the article

• Efficient calculation of matrix cumulative standard deviation in r

  - by Abiel

  I recently posted this question on the r-help mailing list but got no answers, so I thought I would post it here as well and see if there were any suggestions. I am trying to calculate the cumulative standard deviation of a matrix. I want a function that accepts a matrix and returns a matrix of the same size where output cell (i,j) is set to the standard deviation of input column j between rows 1 and i. NAs should be ignored, unless cell (i,j) of the input matrix itself is NA, in which case cell (i,j) of the output matrix should also be NA. I could not find a built-in function, so I implemented the following code. Unfortunately, this uses a loop that ends up being somewhat slow for large matrices. Is there a faster built-in function or can someone suggest a better approach? cumsd <- function(mat) { retval <- mat*NA for (i in 2:nrow(mat)) retval[i,] <- sd(mat[1:i,], na.rm=T) retval[is.na(mat)] <- NA retval } Thanks.

  Read the article

• Division to the nearest 1 decimal place without floating point math?

  - by John Sheares

  I am having some speed issues with my C# program and identified that this percentage calculation is causing a slow down. The calculation is simply n/d * 100. Both the numerator and denominator can be any integer number. The numerator can never be greater than the denominator and is never negative. Therefore, the result is always from 0-100. Right now, this is done by simply using floating point math and is somewhat slow, since it's being calculated tens of millions of times. I really don't need anything more accurate than to the nearest 0.1 percent. And, I just use this calculated value to see if it's bigger than a fixed constant value. I am thinking that everything should be kept as an integer, so the range with 0.1 accuracy would be 0-1000. Is there some way to calculate this percentage without floating point math?

  Read the article

• Adding a calculated field to a Query at run time.

  - by JamesB

  I'm getting data using a query in Delphi, and would like to add a calculated field to the query before it runs. The calculated field is using values in code as well as the query so I can't just calculate it in SQL. I know I can attach an OnCalcFields Event to actually make the calculation, but the problem is after adding the calculated field there are no other fields in the query... I did some digging and found that all of the field defs are created but the actual fields are only created if DefaultFields then CreateFields Default Fields is specified procedure TDataSet.DoInternalOpen; begin FDefaultFields := FieldCount = 0; ... end; Which would indicate that if you add fields you only get the fields you added. I would like all the fields in the query AS WELL AS the ones I Add. Is this possible or do I have to add all the fields I'm using as well?

  Read the article

• How to visually represent file size

  - by Keith Williams

  This will be a bit subjective, I'm afraid, but I'd value the advice of the Collective. Our web application lists documents that users can download; standard file navigator stuff: Type Name Created Size ----------------------------------- PDF Doc 1 01/04/2010 15 KB PDF Doc 2 01/04/2010 15 MB Currently we list the file size as text, but I'd like to improve this by having some way of showing visually whether the file is tiny, normal or huge. The reason for this is so that users can scan the list quickly and spot files that are likely to take a long time downloading. My options currently are: Bigger font sizes for bigger files (drawback: the layout can become untidy) Icons (like a wi-fi signal strength indicator; drawback: harder to scan) Keep all sizes in KB so the number of zeroes indicates size (drawback: users have to calculate the "friendly" size in their heads) I know this is quite a minor thing, but I'd appreciate anyone's thoughts on the matter!

  Read the article

• Will Multi threading increase the speed of the calculation on Single Processor

  - by Harsha

  On a single processor, Will multi-threading increse the speed of the calculation. As we all know that, multi-threading is used for Increasing the User responsiveness and achieved by sepating UI thread and calculation thread. But lets talk about only console application. Will multi-threading increases the speed of the calculation. Do we get culculation result faster when we calculate through multi-threading. what about on multi cores, will multi threading increse the speed or not. Please help me. If you have any material to learn more about threading. please post. Thanks in advance, Harsha

  Read the article

• Implement the Combine function using templates

  - by gkid123

  any idea on how to do it for template? thanks Implement the Combine function using templates. The Combine fn applies a function of two arguments cumulatively to the items of an STL container, from begin() to end(), so as to reduce the sequence to a single value. For example, Combine(<list containing 6,3,1,9,7>, std::plus<int>()) should calculate ((((6+3)+1)+9)+7). class NotEnoughElements {}; template <typename Container, typename Function> typename Container::value_type Combine(const Container& c, Function fn) throw (NotEnoughElements) { your code goes here }

  Read the article

• How to send reminder emails based on users input time and day (based on their time zone)

  - by evgelen

  I need to send emails based on users input time and day (based on their time zone)? Kind of a reminder. For Example: User input 2:00pm Eastern Time on my server I have different time zone, how to calculate the time and send the email at users time-zone. Its a web application. What is the best way to accomplish it using asp.net c#? If somebody already done it in the past I will be glad to take a look at source code. Thank you for useful suggestions.

  Read the article

• changing output in objective-c app

  - by Zack

  // // RC4.m // Play5 // // Created by svp on 24.05.10. // Copyright 2010 __MyCompanyName__. All rights reserved. // #import "RC4.h" @implementation RC4 @synthesize txtLyrics; @synthesize sbox; @synthesize mykey; - (IBAction) clicked: (id) sender { NSData *asciidata1 = [@"4875" dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES]; NSString *asciistr1 = [[NSString alloc] initWithData:asciidata1 encoding:NSASCIIStringEncoding]; //[txtLyrics setText:@"go"]; NSData *asciidata = [@"sdf883jsdf22" dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES]; NSString *asciistr = [[NSString alloc] initWithData:asciidata encoding:NSASCIIStringEncoding]; //RC4 * x = [RC4 alloc]; [txtLyrics setText:[self decrypt:asciistr1 andKey:asciistr]]; } - (NSMutableArray*) hexToChars: (NSString*) hex { NSMutableArray * arr = [[NSMutableArray alloc] init]; NSRange range; range.length = 2; for (int i = 0; i < [hex length]; i = i + 2) { range.location = 0; NSString * str = [[hex substringWithRange:range] uppercaseString]; unsigned int value; [[NSScanner scannerWithString:str] scanHexInt:&value]; [arr addObject:[[NSNumber alloc] initWithInt:(int)value]]; } return arr; } - (NSString*) charsToStr: (NSMutableArray*) chars { NSString * str = @""; for (int i = 0; i < [chars count]; i++) { str = [NSString stringWithFormat:@"%@%@",[NSString stringWithFormat:@"%c", [chars objectAtIndex:i]],str]; } return str; } //perfect except memory leaks - (NSMutableArray*) strToChars: (NSString*) str { NSData *asciidata = [str dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES]; NSString *asciistr = [[NSString alloc] initWithData:asciidata encoding:NSASCIIStringEncoding]; NSMutableArray * arr = [[NSMutableArray alloc] init]; for (int i = 0; i < [str length]; i++) { [arr addObject:[[NSNumber alloc] initWithInt:(int)[asciistr characterAtIndex:i]]]; } return arr; } - (void) initialize: (NSMutableArray*) pwd { sbox = [[NSMutableArray alloc] init]; mykey = [[NSMutableArray alloc] init]; int a = 0; int b; int c = [pwd count]; int d = 0; while (d < 256) { [mykey addObject:[pwd objectAtIndex:(d % c)]]; [sbox addObject:[[NSNumber alloc] initWithInt:d]]; d++; } d = 0; while (d < 256) { a = (a + [[sbox objectAtIndex:d] intValue] + [[mykey objectAtIndex:d] intValue]) % 256; b = [[sbox objectAtIndex:d] intValue]; [sbox replaceObjectAtIndex:d withObject:[sbox objectAtIndex:a]]; [sbox replaceObjectAtIndex:a withObject:[[NSNumber alloc] initWithInt:b]]; d++; } } - (NSMutableArray*) calculate: (NSMutableArray*) plaintxt andPsw: (NSMutableArray*) psw { [self initialize:psw]; int a = 0; int b = 0; NSMutableArray * c = [[NSMutableArray alloc] init]; int d; int e; int f; int g = 0; while (g < [plaintxt count]) { a = (a + 1) % 256; b = (b + [[sbox objectAtIndex:a] intValue]) % 256; e = [[sbox objectAtIndex:a] intValue]; [sbox replaceObjectAtIndex:a withObject:[sbox objectAtIndex:b]]; [sbox replaceObjectAtIndex:b withObject:[[NSNumber alloc] initWithInt:e]]; int h = ([[sbox objectAtIndex:a]intValue] + [[sbox objectAtIndex:b]intValue]) % 256; d = [[sbox objectAtIndex:h] intValue]; f = [[plaintxt objectAtIndex:g] intValue] ^ d; [c addObject:[[NSNumber alloc] initWithInt:f]]; g++; } return c; } - (NSString*) decrypt: (NSString*) src andKey: (NSString*) key { NSMutableArray * plaintxt = [self hexToChars:src]; NSMutableArray * psw = [self strToChars:key]; NSMutableArray * chars = [self calculate:plaintxt andPsw:psw]; NSData *asciidata = [[self charsToStr:chars] dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES]; NSString *asciistr = [[NSString alloc] initWithData:asciidata encoding:NSUTF8StringEncoding]; return asciistr; } @end This is supposed to decrypt a hex string with an ascii string, using rc4 decryption. I'm converting my java application to objective-c. The output keeps changing, every time i run it.

  Read the article

• recursive program

  - by wilson88

  I am trying to make a recursive program that calculates interest per year.It prompts the user for the startup amount (1000), the interest rate (10%)and number of years(1).(in brackets are samples) Manually I realised that the interest comes from the formula YT(1 + R)----- interest for the first year which is 1100. 2nd year YT(1 + R/2 + R2/2) //R squared 2nd year YT(1 + R/3 + R2/3 + 3R3/) // R cubed How do I write a recursive program that will calculate the interest? Below is the function which I tried double calculateInterest(double startUp, double rate, double duration) { double cpdInterest = (duration*startUp)*(1 + rate); if (duration == 0) { return cpdInterest; } else if (duration < 0) { cout << "Please enter a valid year"; } else { calculateInterest(cpdInterest,rate,duration); } return cpdInterest; }

  Read the article

• HTML 5 Canvas - Get pixel data for a path

  - by Mikey S.

  I wonder if is there any way I can get pixel data for the currently drawn path in the canvas tag. I can calculate the pixel data on my own when drawing simple shapes like square or a line, but things get messy with more complicated shapes like ellipse or even a simple circle. The reason i'm asking this is because I'm working on a web application which involves sending canvas pixels data to the server when I add a path to the canvas. The server needs to keep it's own copy of the entire canvas, and I really don't want to send the ENTIRE canvas image every single change, but only the delta for efficiency reasons... Thanks.

  Read the article

• translating ROI code in c#

  - by sayyad

  Hi, I am trying to translate this code in c# using emgucv. I have some questions.Could yome body help me line by line. cvSetImageROI(img1, cvRect(10, 15, 150, 250)); I have four points (PoinstF). Should I calculate rectangle or there is some way with four points. CvInvoke.cvSetImageROI(img1, ------------(how can I declare cvReCt(10, 15, 150, 250)); //c# IplImage *img2 = cvCreateImage(cvGetSize(img1), img1-depth, img1-nChannels); //c# Image img2; // i supose i needn't to allocate memory.//c# cvCopy(img1, img2, NULL); CvInvoke.cvCopy(img1, img2, IntPtr.Zero);//c# cvResetImageROI(img1); shoul i ResetImageROI.//c# thanx and best regards,

  Read the article

• Calculating the union of 2 longitudal intervals (that may wrap around 180 degrees)

  - by timpatt

  The story: I have a LatLongBounds class that represents an area on the surface of the earth by a latitudinal interval (bounded by north & south - not important to this question) and a longitudinal interval (bounded by east and west; both normalized to a range [-180, 180] - negative being a westerly direction). In order to be able to represent an area that straddles the 180 degree meridian the value of west may be set to be greater than east (eg. the range west = 170, east = -170 will straddle said meridian). In effect the longitudinal interval may wrap around at 180 degrees (or equivalently -180 degrees). My Question: Does anyone have any suggestions as to how I can calculate the union of two longitudinal intervals that may wrap around at 180 degrees. Thanks.

  Read the article

• calculating a gps coordinate given a point, bearing and distance

  - by user530509

  Hello, I have a problem which draws my back in some project for some time now. Im basically looking to trap a polygon using x,y points drawn by some script ive written. lat1,lon1 are the center gps cords of the polygon and im looking for its surrounding polygon. here is a part of my code in python: def getcords(lat1,lon1,dr,bearing): lat2=asin(sin(lat1)*cos(dr)+cos(lat1)*sin(dr)*cos(bearing)) lon2=lon1+atan2(sin(bearing)*sin(dr)*cos(lat1),cos(dr)-sin(lat1)*sin(lat2)) return [lat2,lon2] my input goes like this: lat1,lon1 - are given in decimal degrees. -dr is the angular computed by dividing the distance in miles by the earth's -raiuds(=3958.82) -bearing between 0-360 degrees. however for the input getcorsds1(42.189275,-76.85823,0.5/3958.82,30) i get [-1.3485899508698462, -76.8576637627568], however [42.2516666666667,-76.8097222222222] is the right answer. as for the angular distance i calculate it simply by dividing the distance in miles by the earth's raiuds(=3958.82). anybody?

  Read the article

• Randomized experiments in R

  - by gd047

  Here is a simple randomized experiment. In the following code I calculate the p-value under the null hypothesis that two different fertilizers applied to tomato plants have no effect in plants yields. The first random sample (x) comes from plants where a standard fertilizer has been used, while an "improved" one has been used in the plants where the second sample (y) comes from. x <- c(11.4,25.3,29.9,16.5,21.1) y <- c(23.7,26.6,28.5,14.2,17.9,24.3) total <- c(x,y) first <- combn(total,length(x)) second <- apply(first,2,function(x) total[!total %in% x]) dif.treat <- apply(second,2,mean) - apply(first,2,mean) # the first element of dif.treat is the one that I'm interested in (p.value <- length(dif.treat[dif.treat >= dif.treat[1]]) / length(dif.treat)) Do you know of any R function that performs tests like this one?

  Read the article

• Can anyone tell me what's wrong in this part of code

  - by Mobin

  string name = ((DateTimePicker)sender).Name.ToString(); name = name.Substring(0, name.Length - 1); name = name + "4"; TimeSpan duration = new TimeSpan(); duration = ((DateTimePicker)sender).Value - ((DateTimePicker)panel2.Controls[name]).Value; name = name.Substring(0, name.Length - 1); name = name + "6"; ((MaskedTextBox)panel2.Controls[name]).Text = duration.ToString(); On execution it gives me Object reference not set to instance of an object similar functionality is used on other places but I can't find out what I have to reinitialize here :$ The casting for datetimepicker is fine I have to get a name for the datetiempicker to identify the row it's on in my form and the picker before that to calculate their differences and then print that difference in a maskedtext box from the control whose name I make using names of two datetimepickers but when I access controls in the error line I get this message.

  Read the article

• Calculating the pixel size of a string with Python

  - by Aristide

  I have a Python script which needs to calculate the exact size of arbitrary strings displayed in arbitrary fonts in order to generate simple diagrams. I can easily do it with Tkinter. The problem is the results seem to depend on the version of Python and/or the system. import Tkinter as tk import tkFont root = tk.Tk() times12 = tkFont.Font(family="times",size=12) print times12.metrics("linespace"), print times12.measure("Hello world") times24 = tkFont.Font(family="times",size=24) print times24.metrics("linespace"), print times24.measure("Hello world") Python 2.5 on Mac OS X gives the actual pixel measurements: 12 57 24 116 Python 2.6.1 on Mac OS X gives: 14 58 27 115 Python 2.6.3 on Windows XP gives: 19 71 36 154 Such a need being quite common, I suspect I did something wrong. Any idea?

  Read the article

• how to find the max index of a string from variable in c#?

  - by zoya

  suppose i have a string as string[] _strFile; foreach (ListViewItem item in listview1.Items) { string _strRecFileName = item.SubItems[5].Text; _strFile = _strRecFileName.Split('\\'); } in my listview i have a string as \123\abc\hello\.net\*winxp* now i want to get the last value of the string i.e. winxp in this case.. what is the function to do that? can i use getupperbond function to calculate the upper bound of the string and how to use it?

  Read the article

• charts, forms and credit card payment in drupal

  - by mingos

  Hey. I've got this client who's a dietician and wants a site with some functionality I'm not sure how to implement: custom forms that calculate some stuff (like ideal body weight, based on a bazillion factors), the user is supposed to be able to pay for the consultation with a credit card - which lets him access more consultation forms, bi-weekly results from how a user's diet is going (weight reduction and so on) should be displayed using a series of charts, preferably in the user's account page. I use Drupal exclusively, so the question is whether such functionality can be implemented using existing modules? Which modules would you recommend? Can this be achieved without writing custom modules (I've never written a Drupal module)? Thanks in advance for your suggestions.

  Read the article

• How to find control points for a BezierSegment given Start, End, and 2 Intersection Pts in C# - AKA

  - by softwarequestioneer

  Hi, I've been struggling looking for an understandable way to do this. I have four points, a StartPt, EndPoint, and Intersection points to represent the peak and valley in the bezier. The BezierSegment in C# requires start, controlPoint 1, controlPoint 2, endpoint - however I don't have any control points I only have these two points that lie along the bezier curves (i'm calling them intersection points above)... how can I calculate the two control points? Thanks in advance, this has been driving me crazy. There's some kind of explanation here: http://www.tinaja.com/glib/nubz4pts1.pdf but it's written in postscript and that language makes no sense to me at all - it's over my head.

  Read the article

< Previous Page | 68 69 70 71 72 73 74 75 76 77 78 79  | Next Page >