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  • Information Gain and Entropy

    - by dhorn
    I recently read this question regarding information gain and entropy. I think I have a semi-decent grasp on the main idea, but I'm curious as what to do with situations such as follows: If we have a bag of 7 coins, 1 of which is heavier than the others, and 1 of which is lighter than the others, and we know the heavier coin + the lighter coin is the same as 2 normal coins, what is the information gain associated with picking two random coins and weighing them against each other? Our goal here is to identify the two odd coins. I've been thinking this problem over for a while, and can't frame it correctly in a decision tree, or any other way for that matter. Any help? EDIT: I understand the formula for entropy and the formula for information gain. What I don't understand is how to frame this problem in a decision tree format. EDIT 2: Here is where I'm at so far: Assuming we pick two coins and they both end up weighing the same, we can assume our new chances of picking H+L come out to 1/5 * 1/4 = 1/20 , easy enough. Assuming we pick two coins and the left side is heavier. There are three different cases where this can occur: HM: Which gives us 1/2 chance of picking H and a 1/4 chance of picking L: 1/8 HL: 1/2 chance of picking high, 1/1 chance of picking low: 1/1 ML: 1/2 chance of picking low, 1/4 chance of picking high: 1/8 However, the odds of us picking HM are 1/7 * 5/6 which is 5/42 The odds of us picking HL are 1/7 * 1/6 which is 1/42 And the odds of us picking ML are 1/7 * 5/6 which is 5/42 If we weight the overall probabilities with these odds, we are given: (1/8) * (5/42) + (1/1) * (1/42) + (1/8) * (5/42) = 3/56. The same holds true for option B. option A = 3/56 option B = 3/56 option C = 1/20 However, option C should be weighted heavier because there is a 5/7 * 4/6 chance to pick two mediums. So I'm assuming from here I weight THOSE odds. I am pretty sure I've messed up somewhere along the way, but I think I'm on the right path! EDIT 3: More stuff. Assuming the scale is unbalanced, the odds are (10/11) that only one of the coins is the H or L coin, and (1/11) that both coins are H/L Therefore we can conclude: (10 / 11) * (1/2 * 1/5) and (1 / 11) * (1/2) EDIT 4: Going to go ahead and say that it is a total 4/42 increase.

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  • git filter-branch chmod

    - by Evan Purkhiser
    I accidental had my umask set incorrectly for the past few months and somehow didn't notice. One of my git repositories has many files marked as executable that should be just 644. This repo has one main master branch, and about 4 private feature branches (that I keep rebased on top of the master). I've corrected the files in my master branch by running find -type f -exec chmod 644 {} \; and committing the changes. I then rebased my feature branches onto master. The problem is there are newly created files in the feature branches that are only in that branch, so they weren't corrected by my massive chmod commit. I didn't want to create a new commit for each feature branch that does the same thing as the commit I made on master. So I decided it would be best to go back through to each commit where a file was made and set the permissions. This is what I tried: git filter-branch -f --tree-filter 'chmod 644 `git show --diff-filter=ACR --pretty="format:" --name-only $GIT_COMMIT`; git add .' master.. It looked like this worked, but upon further inspection I noticed that the every commit after a commit containing a new file with the proper permissions of 644 would actually revert the change with something like: diff --git a b old mode 100644 new mode 100755 I can't for the life of me figure out why this is happening. I think I must be mis-understanding how git filter-branch works. My Solution I've managed to fix my problem using this command: git filter-branch -f --tree-filter 'FILES="$FILES "`git show --diff-filter=ACMR --pretty="format:" --name-only $GIT_COMMIT`; chmod 644 $FILES; true' development.. I keep adding onto the FILES variable to ensure that in each commit any file created at some point has the proper mode. However, I'm still not sure I really understand why git tracks the file mode for each commit. I had though that since I had fixed the mode of the file when it was first created that it would stay that mode unless one of my other commits explicit changed it to something else. That did not appear to the be the case. The reason I thought that this would work is from my understanding of rebase. If I go back to HEAD~5 and change a line of code, that change is propagated through, it doesn't just get changed back in HEAD~4.

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  • How to get the EJB listening port?

    - by Alotor
    I'm currently developing a library for monitoring calls to several remote services (WebServices, EJBs...). One of the parameters that i would like to register is the port from which a EJB is called (a Stateless Session Bean invoked like a remote object) There is any standarised way of getting the port? Or should I inspect the JNDI tree for this kind of information? I'm using the EJB 2.1 spec, but it's also posible for me to use EJB 3

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  • Objective-C DOM XML parser for iPhone

    - by phunehehe
    Hello guys I'm looking for a way on the iPhone to parse an XML document using DOM. I have been using SAX with NSXMLParser but now I really want a DOM tree (or anything that can quickly translate the XML document into an NSDictionary) Thanks for any help

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  • Sort directory listing using RecursiveDirectoryIterator

    - by Scott Saunders
    I'm using RecursiveDirectoryIterator and RecursiveIteratorIterator to build a file listing tree using code like below. I need to the list to be sorted - either directories then files alphabetically, or just alphabetically. Can anyone tell me how to sort the file list? $dir_iterator = new RecursiveDirectoryIterator($groupDirectory); $iterator = new RecursiveIteratorIterator($dir_iterator, RecursiveIteratorIterator::SELF_FIRST); foreach ($iterator as $file) { // do stuff with $file }

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  • Children in Enumeration

    - by marionmaiden
    Hello I have a enumeration for elements in a JTree When I find some specific element in this JTree, I want to check it's children. Do the method children() in a Enumeration check it's grandcildren too? For example, let's supose this JTree, considering the identation as new levels of the tree: Fruits apple grape orange peach pineapple strawberry banana If I get the children of grape, will I have just orange and peach or will I get peach children (pineaple) too?

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  • Make a Button Appear Focused When Not

    - by Bret
    The Find and Replace dialog in Visual Studio is a perfect example of what im trying to accomplish. Notice how the "Find what" text field has keyboard focus but the "Find Next" button appears bluish as if it has keyboard focus also even though it does not. How can I accomplish this myself? I've tried messing with FocusManager and Focus Scopes without much luck. I suspect i may be barking up the wrong tree? Any advice is appreciated! Thanks

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  • descendeing heap sort

    - by user1
    use heap sort to sort this in descending order and show the steps or explanation please below is the tree 79 33 57 8 25 48 below is the array 79 - 33 - 57 - 8 - 25 - 48

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  • IOS Paypal Phonegap Plugin errors

    - by Paul
    I'm trying to implement the Paypal Plugin for Phonegap (Iphone) - (https://github.com/phonegap/phonegap-plugins/tree/master/iPhone/PayPalPlugin). I've followed all the instructions but I get thefollowing error on build from the SAIOSPaypalPlugin.h file - Lexical or Preprocessor issue - PGPlugin.h not found I'm using latest Cordova version freshly downloaded from Phonegap site just weeks ago, so I'm not sure whats missing?

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  • Sequential numbering from recursive function? e.g. 2, 2.1, 2.1.1, 2.2, 2.2.1

    - by Pete
    I have a recursive function reading a "table of contents" of documents from a database. I would like to print numbering with the document that reflects where the item is in the tree, e.g. First item, 1.1 Child of first item, 1.1.1 Child of child of first item, 1.2 Child of first item, Second item, 2.1 Child of second item, etc. Rather stumped about this at the moment - help please?

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  • Searching temporal data

    - by user321299
    I developing an application (in C#) where objects are active under a period of time, they have from and to properties of DateTime-type. Now I want to speed up my search routine for queries like: Are there other active objects in this timeperiod/at this time. Is there any existing temporal index I can use or can I use QuadTree/other tree-structures to search in an efficient way.

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  • Redirecting page from IFrame to Parent when session expire

    - by Venkatesh
    I have IFrame load one of the menu item click in that page left side I have tree structure and top of the page menu Items.Center of the page loading with IFrame.Whenever session going to expire I am giving alert(session will expire soon). But this alert is coming for Iframe window (after some seconds complete) as well as parent page.That means two alerts are coming whenever session going to expire .That alert should come on parent page not in Iframe page.How to avoid this?

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  • Add to SortedSet<T> and its complexity

    - by Andrei Taptunov
    MSDN states the following SortedSet(T).Add Method : If Count is less than the capacity of the internal array, this method is an O(1) operation. Could someone please explain "how so"? I mean when adding new value we need to find a correct place to add a value (comparing it with another values) and internal implementation looks like a "Red-Black tree" with O (log N) insertion complexity.

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  • video streaming

    - by chima
    i have built a web forum using php but i want to integrate it with videos that are uploaded such that people will be able to make comments on it in a tree view form... how do i integrate that to my php class.....any help with that?

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  • Infinite loop when adding a row to a list in a class in python3

    - by Margaret
    I have a script which contains two classes. (I'm obviously deleting a lot of stuff that I don't believe is relevant to the error I'm dealing with.) The eventual task is to create a decision tree, as I mentioned in this question. Unfortunately, I'm getting an infinite loop, and I'm having difficulty identifying why. I've identified the line of code that's going haywire, but I would have thought the iterator and the list I'm adding to would be different objects. Is there some side effect of list's .append functionality that I'm not aware of? Or am I making some other blindingly obvious mistake? class Dataset: individuals = [] #Becomes a list of dictionaries, in which each dictionary is a row from the CSV with the headers as keys def field_set(self): #Returns a list of the fields in individuals[] that can be used to split the data (i.e. have more than one value amongst the individuals def classified(self, predicted_value): #Returns True if all the individuals have the same value for predicted_value def fields_exhausted(self, predicted_value): #Returns True if all the individuals are identical except for predicted_value def lowest_entropy_value(self, predicted_value): #Returns the field that will reduce <a href="http://en.wikipedia.org/wiki/Entropy_%28information_theory%29">entropy</a> the most def __init__(self, individuals=[]): and class Node: ds = Dataset() #The data that is associated with this Node links = [] #List of Nodes, the offspring Nodes of this node level = 0 #Tree depth of this Node split_value = '' #Field used to split out this Node from the parent node node_value = '' #Value used to split out this Node from the parent Node def split_dataset(self, split_value): fields = [] #List of options for split_value amongst the individuals datasets = {} #Dictionary of Datasets, each one with a value from fields[] as its key for field in self.ds.field_set()[split_value]: #Populates the keys of fields[] fields.append(field) datasets[field] = Dataset() for i in self.ds.individuals: #Adds individuals to the datasets.dataset that matches their result for split_value datasets[i[split_value]].individuals.append(i) #<---Causes an infinite loop on the second hit for field in fields: #Creates subnodes from each of the datasets.Dataset options self.add_subnode(datasets[field],split_value,field) def add_subnode(self, dataset, split_value='', node_value=''): def __init__(self, level, dataset=Dataset()): My initialisation code is currently: if __name__ == '__main__': filename = (sys.argv[1]) #Takes in a CSV file predicted_value = "# class" #Identifies the field from the CSV file that should be predicted base_dataset = parse_csv(filename) #Turns the CSV file into a list of lists parsed_dataset = individual_list(base_dataset) #Turns the list of lists into a list of dictionaries root = Node(0, Dataset(parsed_dataset)) #Creates a root node, passing it the full dataset root.split_dataset(root.ds.lowest_entropy_value(predicted_value)) #Performs the first split, creating multiple subnodes n = root.links[0] n.split_dataset(n.ds.lowest_entropy_value(predicted_value)) #Attempts to split the first subnode.

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  • Java equivalent of C++ std::map?

    - by Rudiger
    I'm looking for a Java class with the characteristics of C++ std::map's usual implementation (as I understand it, a self-balancing binary search tree): O(log n) performance for insertion/removal/search Each element is composed of a unique key and a mapped value Keys follow a strict weak ordering I'm looking for implementations with open source or design documents; I'll probably end up rolling my own support for primitive keys/values. This question's style is similar to: Java equivalent of std::deque, whose answer was "ArrayDeque from Primitive Collections for Java".

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