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• Adjusting for compass wrap around in a navigation application

  - by chris12892

  I have a application where I am guiding a vehicle on compass headings and I am having an issue when the vehicle is crossing from 360 degrees to 0 degrees. In this case, there are no smarts in the control loop to compute that the nearest way to turn to follow a heading. For example, if the vehicle is instructed to follow a heading of 360 degrees, it will inevitably drifts a few degrees to ether side. If it drifts over to 0+ degrees, the control loop will go nuts and try to steer the vehicle all the way around to get it to 360 degrees again. Is there a graceful way to deal with this? The way the navigate function is written, I use an external PID controller class and I calculate the heading like this: lock (steering) { if (!Engaged) { return; } double mv = 90 + Trim + pidController.CalculateCorrection(flyHeading, currentHeading); steering.Degree = mv; } Thanks!

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• Determining if and where a photon will collide with a polygon in 3D space.

  - by Peter

  The problem is straight forward: 1) We have a photon traveling from Point 1 (x,y,z) to Point 2 (x,y,z), both of which could be located anywhere in 3D space. 2) We have a polygon that is both rotated randomly on the x-axis and/or y-axis and also located anywhere in 3D space. 3) We want to find: a) if the photon will collide with the polygon at all and b) if it does where will that be (x,y,z)? An image of the problem: http://dl.dropbox.com/u/3150177/Programming/3D/Math/Photon%20Path/Photon%20Path.png The aim of this is to calculate how the photon's path should be altered from an interaction(s) with the polygon(s). I am reading up on this subject now but I was wondering if anyone could give me a head start. Thanks in advance.

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• Downsampling the number of entries in a list (without interpolation)

  - by Dave

  I have a Python list with a number of entries, which I need to downsample using either: A maximum number of rows. For example, limiting a list of 1234 entries to 1000. A proportion of the original rows. For example, making the list 1/3 its original length. (I need to be able to do both ways, but only one is used at a time). I believe that for the maximum number of rows I can just calculate the proportion needed and pass that to the proportional downsizer: def downsample_to_max(self, rows, max_rows): return downsample_to_proportion(rows, max_rows / float(len(rows))) ...so I really only need one downsampling function. Any hints, please? EDIT The list contains objects, not numeric values so I do not need to interpolate. Dropping objects is fine.

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• filter results quarterly

  - by user339067

  I am writing a simple C# application that is handling bank savings. I want to be able to show the results on either, yearly, monthly or quarterly basic how can this be done? How can I loop through a set of results and only show every third post (if I am using quarterly) for example. In Python I can use range(1,31,3) but how is it done in C#? UPDATE 1 I want to loop 12 times (annually) and calculate the interest each loop but I only want to print the results every third loop (quarterly). How can I achieve this?

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• Calculating percentiles in Excel with "buckets" data instead of the data list itself

  - by G B

  I have a bunch of data in Excel that I need to get certain percentile information from. The problem is that instead of having the data set made up of each value, I instead have info on the number of or "bucket" data. For example, imagine that my actual data set looks like this: 1,1,2,2,2,2,3,3,4,4,4 The data set that I have is this: Value No. of occurrences 1 2 2 4 3 2 4 3 Is there an easy way for me to calculate percentile information (as well as the median) without having to explode the summary data out to full data set? (Once I did that, I know that I could just use the Percentile(A1:A5, p) function) This is important because my data set is very large. If I exploded the data out, I would have hundreds of thousands of rows and I would have to do it for a couple of hundred data sets. Help!

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• Inconsistent values in network switch throughput values

  - by Marcus Hughes

  Quite simple, I have a network switch with SNMP, and need to calculate the throughput of the switch port, so simply I use ifOutOctets. We transfer a file which is 145MB and if we use the total from the start, subtracted from the value at the end then the value is : 158901842 I simply can't get the value to match, or be anything similar to what the real transfer is. I understand that there may be excess traffic etc but I just can't get it to be anywhere similar (the server being tested has no traffic when this is not running) We have tried for a long time and suspect there may be an issue with the recording on the HP switch, do you have any suggestions, or how should we be calculating it? Thanks a lot in advance We have a HP ProCurve 1810G on 2.2

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• Algorithm for calculating indefinite integrals

  - by mbac32768

  Suppose I have an integral that's bounded on one (or both) ends by (-)infinity. AFAICT, I can't analytically solve this problem, it takes brute force (e.g. using a Left Riemann Sum). I'm having trouble generalizing the algorithm so that it sets the proper subdivisions; I'll either do far too much work to calculate something trivial, or not do nearly enough and have huge aliasing errors. Answering in any language is cool, but maybe someone with better google-fu can end this quickly. :) Is what I'm looking for as impossible as trying to measure the British coastline?

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• SQL Server Reporting Services Format Hours as Hours:Minutes

  - by Frank Schmitt

  I'm writing reports on SQL Server Reporting Server that have a number of hours grouped by, say, user, and a total calculated based on the sum of the values. Currently my query runs a stored proc that returns the hours as in HH:MM format, rather than decimal hours, as our users find that more intuitive. The problem occurs when I try and add up the column using an SSRS expression, because the SUM function isn't smart enough to handle adding up times in this format. Is there any way to: Display a time interval (in minutes or hours) in HH:MM format while having it calculated in decimal form? Or split up and calculate the total of the HH:MM text values to arrive at a total as an expression? I'd like to avoid having to write/run a second query just to get the total.

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• Either .each do or .all isn't working how I think it should

  - by user1299656

  So whenever someone rates a shop, I want the Shop model to calculate its new average rating and store that in the database (instead of calculating the average every time someone looks at it). So I wrote the segment of code that follows, and it doesn't work. The loop always iterates exactly once, no matter how many shop_ratings in the database exist that have the shop's id as their shop_id. I played around with it a bit and found that every time a new rating is submitted the function is called successfully, but it only runs the loop once and sets the average to what the first rating was. I don't know if the "query" that sets the ratings variable is wrong or if it's the loop that's wrong. class Shop < ActiveRecord::Base has_many :shop_ratings attr_accessible :name, :latitude, :longitude validates_presence_of :name validates_presence_of :latitude validates_presence_of :longitude def distance_to(lat, long) return (self.longitude - long) + (self.latitude - lat) end def find_average total = 0 count = 0 ratings = ShopRating.all(:conditions => {:shop_id => id}) ratings.each do |submission| total = total + submission.rating count = count + 1 end update_attribute :average_rating, total/count end end

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• MDX filter members in a sum-function

  - by Radagast2005

  I have an SSAS cube containing customers and their purchased memberships (let's say magazines). I want to calculate the retention. I.e. how many customers remain a customer. To do this I specify a set (males, 30yrs, 1 january 2011). I want to see if this set - identified by a customer number - is still present in the following months. I named my set MySet2. What I try to do is: sum(measures.amount, [membership].[name].&[X], MySet2, [date].[date].currentmember) However, the result is incorrect. The number is far to low. I suspect it still tries to account for all the males of 30 years old, but after a year they're not 30 anymore. What am I missing? I looked at scope and filter, but I'm not sure how to apply it.

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• Modulus PHP Problem

  - by Eli

  I have a problem, I am trying to calculate what the lowest prime is of a number but I do not understand the result that PHP is giving me. If I have this number $number = 600851475143; Then I modulus it: $primes = array( 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97); foreach($primes as $key=>$value) { if($number % $value == 0 ) {echo $value; break; } } Why is it that $value = 3? If $value = 3, that means that 600851475143 / 3 should be an integer, but its not. So I do not understand why that if() evaluates to true?

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• Fast, Vectorizable method of taking floating point number modulus of special primes?

  - by caffiend

  Is there a fast method for taking the modulus of a floating point number? With integers, there are tricks for Mersenne primes, so that its possible to calculate y = x MOD 2^31 without needing division. Can any similar tricks be applied for floating point numbers? Preferably, in a way that can be converted into vector/SIMD operations, or moved into GPGPU code. The primes I'm interested in would be 2^7 and 2^31, although if there are more efficient ones for floating point numbers, those would be welcome.

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• How to search for closest value in a lookup table?

  - by CSharperWithJava

  I have a simple one dimmensional array of integer values that represent a physical set of part values I have to work with. I then calculate and ideal value mathematically. How could I write an efficient search algorithm that will find the smallest abosulte difference from my ideal value in the array? The array is predetermined and constant, so it can be sorted however I need. Example Lookup array: 100, 152, 256, 282, 300 Searching for an ideal value of 125 would find 100 in the array, whereas 127 would find 152. The actual lookup array will be about 250 items long and never change.

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• Fibonacci Numbers in Haskell

  - by boraer

  Hi everbody I need to change my F# code to Haskell code but I am so new in Haskell and I can not this My code simply read data from keyboard if data not an integer return an error message then calculate the n fibonacci number then writes to a list after that writes the list into a txt file Here is my code open System let rec fib n = match n with |0->0 |1->1 |2->1 |n->fib(n-1)+fib(n-2);; let printFibonacci list = for i=0 to (List.length list)-1 do printf "%d " (list.Item(i));; let writeToFile list = let file = System.IO.File.Create("C:\out2.txt") let mutable s ="" let writer = new System.IO.StreamWriter(file) try for i=0 to (List.length list)-1 do s <- list.Item(i).ToString() writer.Write(s+" ") finally writer.Close() file.Dispose() printfn "Writed To File" let mutable control = true let mutable num = 0 while control do try printfn "Enter a Number:" num <- Convert.ToInt32(stdin.ReadLine()) let listFibonacci = [for i in 0 .. num-1->fib(i)] printFibonacci(listFibonacci) printfn "\n%A"(listFibonacci) writeToFile(listFibonacci) control<-false with | :? System.FormatException->printfn "Number Format Exception"; Console.ReadKey true|>ignore

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• android, find the nearest location without going through all the locations

  - by Marwan

  I am building a taxi dispatching app first: I need the passenger app to show the nearest taxis, now I know how to do that in code but in my way I have to go through all the taxis locations(in database on server) and calculate the distance from the passenger location and get the lowest ones - I don't want to do this because there will be a lot of taxis and going through all of them and making some math is kind of pain on the server- is there a way to get the nearest ones without going through all of them? second: what the best database to use - first, should it be sql or non-sql - I need a very robust database, because there will be a lot of updates (I mean the passengers locations added then deleted when arriving to destination && the taxis location changes frequently) finally: I will use RubyOnRails to do the server side and json as data transfer format, do you have a recommendation to me on something better? Thanks

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• Get label height for fixed width

  - by Jonas

  Is there any way I can get the height of a label, if it hypothetically had a certain width? I've been trying with control.GetPreferredSize(size) like so: Dim wantedWidth as Integer = 100 dim ctrlSize as Size = label.GetPreferredSize(new Size(wantedWidth, 0)) because I thought that setting height = 0, would indicate a free height, but the height I get is way too small. I also tried to estimate the height of the label, using Graphics.MeasureString to calculate the equivalent area of the Label dim prefWidth as Integer = 100 dim estSize as SizeF = g.MeasureString(label.Text, label.Font) dim estHeight as Integer = (Integer)(estSize.Width * estSize.Height / prefWidth) but that yields the same result. Any ideas? I'm on .NET 2.0, unfortunately.

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• How can I make the output from tapply() into a data.frame

  - by James Thompson

  I have a data.frame in R that looks like this: score rms template aln_id description 1 -261.410 4.951 2f22A.pdb 2F22A_1 S_00001_0000002_0 2 -231.987 21.813 1wb9A.pdb 1WB9A_4 S_00002_0000002_0 3 -263.722 4.903 2f22A.pdb 2F22A_3 S_00003_0000002_0 4 -269.681 17.732 1wbbA.pdb 1WBBA_6 S_00004_0000002_0 5 -258.621 19.098 1rxqA.pdb 1RXQA_3 S_00005_0000002_0 6 -246.805 6.889 1rxqA.pdb 1RXQA_15 S_00006_0000002_0 7 -281.300 16.262 1wbdA.pdb 1WBDA_11 S_00007_0000002_0 8 -271.666 4.193 2f22A.pdb 2F22A_2 S_00008_0000002_0 9 -277.964 13.066 1wb9A.pdb 1WB9A_5 S_00009_0000002_0 10 -261.024 17.153 1yy9A.pdb 1YY9A_2 S_00001_0000003_0 I can calculate summary statistics on the data.frame like this: > tapply( d$score, d$template, mean ) 1rxqA.pdb 1wb9A.pdb 1wbbA.pdb 1wbdA.pdb 1yy9A.pdb 2f22A.pdb -252.7130 -254.9755 -269.6810 -281.3000 -261.0240 -265.5993 Is there an easy way that I coerce this output back into a data.frame? I'd like for it to have these two columns: d$template mean I love tapply, but right now I'm cutting and pasting the results from tapply into a text file and hacking it up a bit to get the summary statistics that I want with appropriate names. This feels very wrong, and I'd like to do something better!

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• 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 //Latest after editing double calculateInterest2(double start, double rate, int duration) { if (0 == duration) { return start; } else { return (1+rate) * calculateInterest2(start, rate, duration - 1); } }

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• Do there any dev who wrote iPhone wifi/bluetooth multiplay before?

  - by Jerry1923

  Hi there, do there any dev who wrote iPhone wifi/bluetooth multiplay before? Recently, I'm trying to make my latest game Doodle Kart to have mulityplay via bluetooth. But I found that there are hugh data need to share between the 2 devices. -your car's position and direction -your car's status(it is in normal state, it is hitting by bullet, it is falling into to hole....) -CUP car's position, dicretion, and their status -items position and status (pencil, bullet...) I'm thinking about one device calculate all the things, and the other device just wait and receive the data to display on the screen. Does it make sense? Hey, I should ask you the most important question first: Do you think it's possible to make bluetooth multiplay work on my game? It's just too much data need to share between the device.

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• Looking for a way to draw a line between two points on a sphere in Three.js

  - by speedwell

  My app (a flight tracker) needs to draw a line between two points (cities say) on a sphere (earth) along the surface (i.e. the great circle route) using Three.js. I can think of 2 ways - (a) creating Three.js 'Line' with a set of (enough) points that I calculate manually and (b) writing the lines into the texture I use for the sphere after it's loaded but before I apply it as a texture. I can see problems with both (not even sure if (b) is possible in Three.js yet) - anyone think of a better way or have an opinion? Thanks in advance.

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• python len calculation

  - by n00bz0r

  I'm currently trying to build a RDP client in python and I came across the following issue with a len check; From: http://msdn.microsoft.com/en-us/library/cc240836%28v=prot.10%29.aspx "81 2a - ConnectData::connectPDU length = 298 bytes Since the most significant bit of the first byte (0x81) is set to 1 and the following bit is set to 0, the length is given by the low six bits of the first byte and the second byte. Hence, the value is 0x12a, which is 298 bytes." This sounds weird. For normal len checks, I'm simply using : struct.pack("h",len(str(PacketLen))) but in this case, I really don't see how I can calculate the len as described above. Any help on this would be greatly appreciated !

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• How to test Text Search accuracy and efficiency?

  - by DEN

  I have created a web application. One of the feature is text search which perform the boolean operator ( NOT, AND, OR) as well. However, I have no idea on calculating the search's accuracy and efficiency. For example: 1 . Probe identification system for a measurement instrument 2 . Pulse-based impedance measurement instrument 3 . Millimeter with filtered measurement mode when the user key in will return the result as below input :measurement instrument Result: 1,2 input : measurement OR instrument NOT milimeter Result: 1,2,3 so, i have no idea on what issue and what algorithm to calculate on the accuracy and efficiency of the text search.. anyone have any idea on that?

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• optimized grid for rectangular items

  - by peterchen

  I have N rectangular items with an aspect ratio Aitem (X:Y). I have a rectangular display area with an aspect ratio Aview The items should be arranged in a table-like layout (i.e. r rows, c columns). what is the ideal grid rows x columns, so that individual items are largest? (rows * colums = N, of course - i.e. there may be "unused" grid places). A simple algorithm could iterate over rows = 1..N, calculate the required number of columns, and keep the row/column pair with the largest items. I wonder if there's a non-iterative algorithm, though (e.g. for Aitem = Aview = 1, rows / cols can be approximated by sqrt(N)).

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• how to get dynamically created elements width and apply style to that?

  - by 3gwebtrain

  Hi, I am creating an li element dynamically like this: $(data).find('slide').each(function(numSlide){ var slideLink = $(this).attr('link'); var slideimage = $(this).children('slideimage').text(); var slidedesc = $(this).children('slidedesc').text(); $('.slider ul').append('<li><a href="'+slideLink+'"><img src="'+root+"images/top-slider-image/"+slideimage+'" alt="welcome to Burger Davis Blog" /></a><div class="note">'+slidedesc+'</div></li>'); }) But I'd like to calculate the width of the li, and I need to apply some style to it -- how can I do that? If I add styles via the css method, it does not work for dynamically created elements... Please help me to get dynamic elements' width and how to apply styles into that? I know we can use the live function, but I can't get even by that..

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• Python breaks for a certain amount

  - by Brian Cox

  All, I am not very good at explaining so i will let my comments do it! #this script is to calculate some of the times table up to 24X24 and also miss some out #Range of numbers to be calculated numbers=range(1,25) for i in numbers: for w in numbers: print(str(i)+"X"+str(w)+"="+str(i*w)) #here i want to break randomly (skip some out) e.g. i could be doing the 12X1,12X2 and then 12X5 i have no limit of skips. Update Sorry if this is not clear i want it to break from the inner loop for a random amount of times

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