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• Explaining training method for AdaBoost algorithm

  - by konzti8

  Hi, I'm trying to understand the Haar feature method used for the training step in the AdaBoost algorithm. I don't understand the math that well so I'd appreciate more of a conceptual answer (as much as possible, anyway). Basically, what does it do? How do you choose positive and negative sets for what you want to select? Can it be generalized? What I mean by that is, can you choose it to find any kind of feature that you want no matter what the background is? So, for example, if I want to find some kind of circular blob - can I do that? I've also read that it is used on small patches for the images around the possible feature - does that mean you have to manually select that image patch or can it be automated to process the entire image? Is there matlab code for the training step? Thanks for any help...

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• Problem with truncation of floating point values in DBSlayer.

  - by chrisdew

  When I run a query through DBslayer http://code.nytimes.com/projects/dbslayer the floating point results are truncated to a total of six digits (plus decimal point and negative sign when needed). { ... "lat":52.2228,"lng":-2.19906, ... } When I run the same query in MySQL, the results are as expected. | 52.22280884 | -2.19906425 | Firstly, am I correct in identifying DBSlayer as the cause of this effect? (Or the JSON library it uses, etc.) Secondly, is this floating point precision configurable within DBSlayer? Thanks, Chris. P.S. Ubuntu 9.10, x86_64 Path: . URL: http://dbslayer.googlecode.com/svn/trunk Repository Root: http://dbslayer.googlecode.com/svn Repository UUID: 5df2be84-4748-0410-afd4-f777a056bd0c Revision: 65 Node Kind: directory Schedule: normal Last Changed Author: dgottfrid Last Changed Rev: 65 Last Changed Date: 2008-03-28 22:52:46 +0000 (Fri, 28 Mar 2008)

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• Graphing a line and scatter points using Matplotlib?

  - by Patrick O'Doherty

  Hi guys I'm using matplotlib at the moment to try and visualise some data I am working on. I'm trying to plot around 6500 points and the line y = x on the same graph but am having some trouble in doing so. I can only seem to get the points to render and not the line itself. I know matplotlib doesn't plot equations as such rather just a set of points so I'm trying to use and identical set of points for x and y co-ordinates to produce the line. The following is my code from matplotlib import pyplot import numpy from pymongo import * class Store(object): """docstring for Store""" def __init__(self): super(Store, self).__init__() c = Connection() ucd = c.ucd self.tweets = ucd.tweets def fetch(self): x = [] y = [] for t in self.tweets.find(): x.append(t['positive']) y.append(t['negative']) return [x,y] if __name__ == '__main__': c = Store() array = c.fetch() t = numpy.arange(0., 0.03, 1) pyplot.plot(array[0], array[1], 'ro', t, t, 'b--') pyplot.show() Any suggestions would be appreciated, Patrick

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• Does JUnit4 testclasses require a public no arg constructor?

  - by Thomas Baun

  I have a test class, written in JUnit4 syntax, that can be run in eclipse with the "run as junit test" option without failing. When I run the same test via an ant target I get this error: java.lang.Exception: Test class should have public zero-argument constructor at org.junit.internal.runners.MethodValidator.validateNoArgConstructor(MethodValidator.java:54) at org.junit.internal.runners.MethodValidator.validateAllMethods(MethodValidator.java:39) at org.junit.internal.runners.TestClassRunner.validate(TestClassRunner.java:33) at org.junit.internal.runners.TestClassRunner.<init>(TestClassRunner.java:27) at org.junit.internal.runners.TestClassRunner.<init>(TestClassRunner.java:20) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at org.junit.internal.requests.ClassRequest.getRunner(ClassRequest.java:26) at junit.framework.JUnit4TestAdapter.<init>(JUnit4TestAdapter.java:24) at junit.framework.JUnit4TestAdapter.<init>(JUnit4TestAdapter.java:17) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.run(JUnitTestRunner.java:386) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.launch(JUnitTestRunner.java:911) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.main(JUnitTestRunner.java:768) Caused by: java.lang.NoSuchMethodException: dk.gensam.gaia.business.bonusregulering.TestBonusregulerAftale$Test1Reader.<init>() at java.lang.Class.getConstructor0(Class.java:2706) at java.lang.Class.getConstructor(Class.java:1657) at org.junit.internal.runners.MethodValidator.validateNoArgConstructor(MethodValidator.java:52) I have no public no arg constructor in the class, but is this really necessary? This is my ant target <target name="junit" description="Execute unit tests" depends="compile, jar-test"> <delete dir="tmp/rawtestoutput"/> <delete dir="test-reports"/> <mkdir dir="tmp/rawtestoutput"/> <junit printsummary="true" failureproperty="junit.failure" fork="true"> <classpath refid="class.path.test"/> <classpath refid="class.path.model"/> <classpath refid="class.path.gui"/> <classpath refid="class.path.jfreereport"/> <classpath path="tmp/${test.jar}"></classpath> <batchtest todir="tmp/rawtestoutput"> <fileset dir="${build}/test"> <include name="**/*Test.class" /> <include name="**/Test*.class" /> </fileset> </batchtest> </junit> <junitreport todir="tmp"> <fileset dir="tmp/rawtestoutput"/> <report todir="test-reports"/> </junitreport> <fail if="junit. failure" message="Unit test(s) failed. See reports!"/> </target> The test class have no constructors, but it has an inner class with default modifier. It also have an anonymouse inner class. Both inner classes gives the "Test class should have public zero-argument constructor error". I am using Ant version 1.7.1 and JUnit 4.7

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• Simple but efficient way to store a series of small changes to an image?

  - by finnw

  I have a series of images. Each one is typically (but not always) similar to the previous one, with 3 or 4 small rectangular regions updated. I need to record these changes using a minimum of disk space. The source images are not compressed, but I would like the deltas to be compressed. I need to be able to recreate the images exactly as input (so a lossy video codec is not appropriate.) I am thinking of something along the lines of: Composite the new image with a negative of the old image Save the composited image in any common format that can compress using RLE (probably PNG.) Recreate the second image by compositing the previous image with the delta. Although the images have an alpha channel, I can ignore it for the purposes of this function. Is there an easy-to-implement algorithm or free Java library with this capability?

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• Overwriting arguments object for a Javascript function

  - by Ian Storm Taylor

  If I have the following: // Clean input. $.each(arguments, function(index, value) { arguments[index] = value.replace(/[\W\s]+/g, '').toLowerCase(); }); Would that be a bad thing to do? I have no further use for the uncleaned arguments in the function, and it would be nice not to create a useless copy of arguments just to use them, but are there any negative effects to doing this? Ideally I would have done this, but I'm guessing this runs into problems since arguments isn't really an Array: arguments = $.map(arguments, function(value) { return value.replace(/[\W\s]+/g, '').toLowerCase(); }); Thanks for any input. EDIT: I've just realized that both of these are now inside their own functions, so the arguments object has changed. Any way to do this without creating an unnecessary variable?

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• Compact a given array problem

  - by Bragaadeesh

  Dont know whether this is a duplicate, but this was an interview question asked to me. Given an array of random numbers and -1 placed inbetween, I have to compact the array meaning all the -1s are to be replaced and the final output should be the last valid index with the fresh array. For example. Input: 3 4 -1 -1 -1 5 8 -1 8 Output: 3 4 5 8 8 5 8 -1 8 and last valid index is 4 Input: -1 -1 -1 -1 -1 2 Output: 2 -1 -1 -1 -1 2 and last valid index is 0 Input: -1 -1 -1 3 3 3 Output: 3 3 3 3 3 3 and last valid index is 2 You should not swap the values just the last valid index along with the array is enough to decipher the non negative values.

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• How do I apply css for textboxes only but not for all the <input> types like CheckBoxes, etc.?

  - by George

  If all browsers supported attribute selectors, we could easily do the following: input[type='text'] { font:bold 0.8em 'courier new',courier,monospace; } input[type='radio'] { margin:0 20px; } input[type='checkbox'] { border:2px solid red; But I don't think all IE versions of ^ and greater support this. I think I'd like to avoid skins. Not sure why, other than I tried them and I recall having a negative experience. It was probably my lack of knowledge. Are there any issues in using and CSS, external or otherwise? What's the best way to handle this? Currently I am assigning separate classes to each control type.

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• Strange padding in Safari when using SVG images

  - by Naman Goel

  I thought I was having issues with margins but then on a closer look I found that SVGs are acting funky in Safari 6. I am building a simple Hexagon based website. Of course I used negative vertical margins to for a little overlap to 'inter-lock' the hexagons. And to save space I was using SVG images for the hexagons. It works great in chrome and firefox, but in Safari, there is a strange padding in the SVG images. I'm using simple img tags for the svg images. Everything works when I switch to PNG, but I'd prefer to stick to SVGs. Any insight? Can I perhaps delve into the SVG code and somehow fix the SVG problem in Safari? or is it some sort of bug, that I can do nothing about without browser sniffing?

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• A specific string format with a number and character together represeting a certain item

  - by sil3nt

  Hello there, I have a string which looks like this "a 3e,6s,1d,3g,22r,7c 3g,5r,9c 19.3", how do I go through it and extract the integers and assign them to its corresponding letter variable?. (i have integer variables d,r,e,g,s and c). The first letter in the string represents a function, "3e,6s,1d,3g,22r,7c" and "3g,5r,9c" are two separate containers . And the last decimal value represents a number which needs to be broken down into those variable numbers. my problem is extracting those integers with the letters after it and assigning them into there corresponding letter. and any number with a negative sign or a space in between the number and the letter is invalid. How on earth do i do this?

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• Graphics/Bitmap Limits?

  - by Dean

  Im having some weird problems with Graphics and Bitmap. I have a Graphics Object that is displayed on a PictureBox and im capturing the MouseMove and MouseClick Events that give X and Y Position of the Mouse on the Image but if the Y Position goes Bigger then 32775 it then goes into Negatives which means everything breaks. And if the Image is Bigger then 65535 it then stops displaying the Image. Any Ideas how these problems can be fixed? Thanks Example Code: http://pastebin.com/YEX0XD1q Just Click Make 10,000 Bigger about 4 times then scroll down and on the right it will show the mouse X and Y position and as you move down through the image and hover over the Red Area if you go down enough it will go into Negative Y.

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• Faith and Godaddy [closed]

  - by yuval

  Let's remove the capitalizations from the name GoDaddy - the hosting company: godaddy. Now let's look at the spacing a little differently: god addy, and capitalize: God Addy: God Addy: The address of God Did anybody notice this? How many negative votes will this question get? How long until someone closes the discussion on this question? All of this and more... NOW! Someone favorited this! woo! In addition to my serious and intelligent previous question: Who came first, the chicken or the egg?

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• Accelerometer Values from Android/iPhone device

  - by mrlinx

  I'm trying to map my movements with a android device into an OpenGL scene. I've recorded accelerometer values for a simples movement: Moving the phone (lies flat on a table) 10cm forward (+x), and then 10cm backward (-x). The problem is that this values when used to calculate velocity and position, makes only the opengl cube go forward. Seems like the negative acceleration recorded was not enough to reduce the speed and invert its movement. What can be the problem? This is my function that updates the velocity and position every time new data comes in: void updatePosition(double T2) { double T = 0.005; Vec3 old_pos = position.clone(), old_vel = velocity.clone(); velocity = old_vel.plus(acceleration.times(T)); position = old_pos.plus(old_vel.times(T).plus(acceleration.times(0.5 * Math.pow(T, 2)))); } This is the X,Y,Z accelerometer values over the entire captured time:

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• Difference of two 'uint'

  - by vanslly

  When you attempt to declare an unsigned variable in C#.NET with a value outside its value range it is flagged as a compiler error, but if you produce a negative value at runtime and assign it to that variable at runtime the value wraps. uint z = -1; // Will not compile uint a = 5; uint b = 6; uint c = a - b; // Will result in uint.MaxValue Is there a good reason why unsigned variables wrap in such a situation instead of throwing an exception? Thanks.

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• Efficient representation of Hierarchies in Hibernate.

  - by Alison G

  I'm having some trouble representing an object hierarchy in Hibernate. I've searched around, and haven't managed to find any examples doing this or similar - you have my apologies if this is a common question. I have two types which I'd like to persist using Hibernate: Groups and Items. * Groups are identified uniquely by a combination of their name and their parent. * The groups are arranged in a number of trees, such that every Group has zero or one parent Group. * Each Item can be a member of zero or more Groups. Ideally, I'd like a bi-directional relationship allowing me to get: * all Groups that an Item is a member of * all Items that are a member of a particular Group or its descendants. I also need to be able to traverse the Group tree from the top in order to display it on the UI. The basic object structure would ideally look like this: class Group { ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { ... } /** @return all direct children of this group */ Set<Group> getChildren() { ... } ... } class Item { ... /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { ... } ... } Originally, I had just made a simple bi-directional many-to-many relationship between Items and Groups, such that fetching all items in a group hierarchy required recursion down the tree, and fetching groups for an Item was a simple getter, i.e.: class Group { ... private Set<Item> items; private Set<Group> children; ... /** @return all items in this group and its descendants */ Set<Item> getAllItems() { Set<Item> allItems = new HashSet<Item>(); allItems.addAll(this.items); for(Group child : this.getChildren()) { allItems.addAll(child.getAllItems()); } return allItems; } /** @return all direct children of this group */ Set<Group> getChildren() { return this.children; } ... } class Item { ... private Set<Group> groups; /** @return all groups that this Item is a direct member of */ Set<Group> getGroups() { return this.groups; } ... } However, this resulted in multiple database requests to fetch the Items in a Group with many descendants, or for retrieving the entire Group tree to display in the UI. This seems very inefficient, especially with deeper, larger group trees. Is there a better or standard way of representing this relationship in Hibernate? Am I doing anything obviously wrong or stupid? My only other thought so far was this: Replace the group's id, parent and name fields with a unique "path" String which specifies the whole ancestry of a group, e.g.: /rootGroup /rootGroup/aChild /rootGroup/aChild/aGrandChild The join table between Groups and Items would then contain group_path and item_id. This immediately solves the two issues I was suffering previously: 1. The entire group hierarchy can be fetched from the database in a single query and reconstructed in-memory. 2. To retrieve all Items in a group or its descendants, we can select from group_item where group_path='N' or group_path like 'N/%' However, this seems to defeat the point of using Hibernate. All thoughts welcome!

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• Caption in longtable

  - by Tim

  Hi, I find that the caption in my longtable takes two lines but it seems that it can fit in one line. See the figure below: http://i42.tinypic.com/96dqms.jpg My code is: \begin{longtable}{|c|c|c|c||c|c|c|} \caption{Testing error for training size 100000 and 8000 random counts\label{tab:1}}\\ \hline \multicolumn{2}{|c|}{Concept} & \multicolumn{2}{c||}{Negative Class} & \multicolumn{2}{c|}{Positive Class} & Error rate \\ \hline ... \end{longtable} How to make the caption fit into a single line? Thanks and regards!

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• Is -1 a magic number? An anti-pattern? A code smell? Quotes and guidelines from authorities

  - by polygenelubricants

  I've seen -1 used in various APIs, most commonly when searching into a "collection" with zero-based indices, usually to indicate the "not found" index. This "works" because -1 is never a legal index to begin with. It seems that any negative number should work, but I think -1 is almost always used, as some sort of (unwritten?) convention. I would like to limit the scope to Java at least for now. My questions are: What are the official words from Sun regarding using -1 as a "special" return value like this? What quotes are there regarding this issue, from e.g. James Gosling, Josh Bloch, or even other authoritative figures outside of Java? What were some of the notable discussions regarding this issue in the past?

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• Back Orders for ERP: data model references ?

  - by Patrick Honorez

  I have built an ERP using Sql Server as a back-end. These are the different types of Client documents (there are also Supplier Docs): Order -- impact: BO Delivery Note (also used for returns, with negative quantity) --impact: BO, Stock Invoice --impact: accounting only Credit Note --impact: accounting, BO I use a complex system of self joins (at detail level) to find out the quantities in each OrderDetail that still have a backorder (BO). It'd like to simplify this using a [group] field that could be used through all detail line related to an original order. There are many difficult things to trace: a Return of a product may be due to a defect and thus increase the BO, or it can be just a return, joined with a Credit Note, and then has no impact on BO. My question is: do you know of any real good reference (book, web) for this matter ?

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• How does c# type safety affect the garbage collection?

  - by Indeera

  I'm dealing with code that handles large buffers ( 100MB) and manipulation of these is done in unsafe blocks. I'd like to refactor these to avoid unsafe code. I'm wondering about the likely memory performance gains (positive/negative/neutral) before I embark on that. I assert that if the compiler can verify types, it could possibly generate better code and that could also mean good GC performance. Is this a valid assertion? What is your experience? Thanks.

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• Sorting an array in descending order in Ruby.

  - by Waseem

  Hi, I have an array of hashes like following [ { :foo => 'foo', :bar => 2 }, { :foo => 'foo', :bar => 3 }, { :foo => 'foo', :bar => 5 }, ] I am trying to sort above array in descending order according to the value of :bar in each hash. I am using sort_by like following to sort above array. a.sort_by { |h| h[:bar] } However above sorts the array in ascending order. How do I make it sort in descending order? One solution was to do following: a.sort_by { |h| -h[:bar] } But that negative sign does not seem appropriate. Any views?

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• C#. Whats the fastest way to make an integer positive

  - by maxima120

  I asked wrong question previously and was swamped with negative votes... Let me try again... What is absolutely fastest way to make an int positive (given 50/50 distribution of pos/neg over time). To be nominated for an answer I will require MSIL analysis and not a guess or measuring of time with granny's watch... P.S. as one of variations I proposed i * i not because I wanted to do Sqrt(i * i) afterwards but because i will be used only once to be compared to a const. And if i * i will win competition I simply multiply the const.. Hence the following solution is valid: int trigger = realTrigger * realTrigger; i = SomeCalcs(); i = i * i; if(i < trigger) DoSomething(); P.P.S. pointless rant is not acceptable.. like: why do you need this, its BS! C# cannot tolerate developers like you!

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• What is the safest way to subtract two System.Runtime.InteropServices.ComTypes.FILETIME objects

  - by Anindya Chatterjee

  I wonder what is the safest way to subtract two System.Runtime.InteropServices.ComTypes.FILETIME objects? I used the following code but sometimes it gives me ArithmaticOverflow exception due to the negative number in Low 32-bit values. I am not sure enclosing the body with unchecked will serve the purpose or not. Please give me some suggestion on how to do it safely without getting any runtime exception or CS0675 warning message. private static UInt64 SubtractTimes(FILETIME a, FILETIME b) { UInt64 aInt = ((UInt64)(a.dwHighDateTime << 32)) | (UInt32)a.dwLowDateTime; UInt64 bInt = ((UInt64)(b.dwHighDateTime << 32)) | (UInt32)b.dwLowDateTime; return aInt - bInt; }

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• minimum enclosing rectangle of fixed aspect ratio

  - by Ramya Narasimha

  I have an Image with many rectangles at different positions in the image and of different sizes (both overlapping and non-overlapping). I also have a non-negative scores associated with each of these rectangles. My problem now is to find one larger rectangle *of a fixed (given) aspect ratio* that encloses as many of these rectangles as possible. I am looking for an algorithm to do this, if anyone has a solution, even a partial one it would be helpful. Please note that the positions of the rectangles in the image is fixed and cannot be moved around and there is no orientation issue as all of them are upright.

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• Adjust price to demand: Simplest way

  - by marco92w

  For a game I need to adjust a price to the given demand. There's a shop which sells one item. If lots of people buy the item, the price should increase. If less people buy it, the price should decrease. How could I achieve this? This is just a little part of the game so I don't need a perfect solution. Just a very easy solution which does it so that the price is adjusted. Something like this: For every sold item, increase the price by 1,000 On every day, decrease the price by 1,500 (only one time) Don't let the price become negative Thank you very much in advance!

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• Regex pattern for searches with include and exclude

  - by alex-kravchenko-zmeyp

  I am working on a Regex pattern for searches that should allow optional '+' sign to include in the search and '-' sign to exclude from the search. For example: +apple orange -peach should search for apples and oranges and not for peaches. Also the pattern should allow for phrases in double quotes mixed with single words, for example: "red apple" -"black grape" +orange - you get the idea, same as most of the internet searches. So I am running 2 regular expressions, first to pick all the negatives, which is simple because '-' is required: (?<=[\-]"?)((?<=")(?<exclude>[^"]+)|(?<exclude>[^\s,\+\-"]+)) And second to pick positives, and it is a little more complex because '+' is optional: ((?<=[\+\s]")(?<include>[^\s"\+\-][^"]+))|(?<include>(?<![\-\w]"?)([\w][^,\s\-\+]+))(?<!") Positive search is where I am having a problem, it works fine when I run it in RegexBuddy but when I try in .Net the pattern picks up second word from negative criteria, for example in -"black grape" it picks up word 'grape' even though it ends with double quote. Any suggestions?

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