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• how do i see if a big JSON object contains a value?

  - by Haroldo

  I'm using PHP to json encode a massive multi-dimensional array of events, so i get something like this: var ents = {"7":{"event_id":"7","nn":"The Whisky Drifters","nn_url":"the-whisky-drifters","venue":"The Grain Barge","date_num":"2010-06-11","date_txt":"Friday 11th June","gig_club":"1","sd":"A New Acoustic String Band...","ven_id":"44","art":0},"15":{"event_id":"15","nn":"Bass Kitchen","nn_url":"bass-kitchen","venue":"Timbuk2","date_num":"2010-06-11","date_txt":"Friday 11th June","gig_club":"2","sd":"Hexadecimal \/ DJ Derek \/ Id","ven_id":"21","art":1}, the first dimension is the id, see var ents = {"7":{ So its possible to get the ids without examining the nested objects... What's the fastest, most efficent way to check if my JSON contains an id?

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• SQL partial max

  - by Rob

  Struggling with the following SQL problem Assume a three dimensional table with entries (h,t,q) 1,A,20 1,A,10 1,B,5 2,A,10 2,B,3 2,B,8 3,C,50 4,A,10 etc. I would like to extract 1,30 2,11 3,50 etc. group by first element and then return the maximum q value of same type, i.e. for header number 2 there are 10 As and 11 Bs, so return 11 The "max" element (A in case 1, B in case 2 and C in case 3) is irrelevant, I just need to get out the header and that maximum value. This shouldnt be too tricky, but cant get it to work. Using MS Access, but can use SQL within.

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• How do I sum up weighted arrays in PHP?

  - by christian studer

  Hod do I multiply the values of a multi-dimensional array with weigths and sum up the results into a new array in PHP or in general? The boring way looks like this: $weights = array(0.25, 0.4, 0.2, 0.15); $values = array ( array(5,10,15), array(20,25,30), array(35,40,45), array(50,55,60) ); $result = array(); for($i = 0; $i < count($values[0]); ++$i) { $result[$i] = 0; foreach($weights as $index => $thisWeight) $result[$i] += $thisWeight * $values[$index][$i]; } Is there a more elegant solution?

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• Find the closest vector

  - by Alexey Lebedev

  Hello! Recently I wrote the algorithm to quantize an RGB image. Every pixel is represented by an (R,G,B) vector, and quantization codebook is a couple of 3-dimensional vectors. Every pixel of the image needs to be mapped to (say, "replaced by") the codebook pixel closest in terms of euclidean distance (more exactly, squared euclidean). I did it as follows: class EuclideanMetric(DistanceMetric): def __call__(self, x, y): d = x - y return sqrt(sum(d * d, -1)) class Quantizer(object): def __init__(self, codebook, distanceMetric = EuclideanMetric()): self._codebook = codebook self._distMetric = distanceMetric def quantize(self, imageArray): quantizedRaster = zeros(imageArray.shape) X = quantizedRaster.shape[0] Y = quantizedRaster.shape[1] for i in xrange(0, X): print i for j in xrange(0, Y): dist = self._distMetric(imageArray[i,j], self._codebook) code = argmin(dist) quantizedRaster[i,j] = self._codebook[code] return quantizedRaster ...and it works awfully, almost 800 seconds on my Pentium Core Duo 2.2 GHz, 4 Gigs of memory and an image of 2600*2700 pixels:( Is there a way to somewhat optimize this? Maybe the other algorithm or some Python-specific optimizations.

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• How to convert an HTML table to an array in python

  - by user345660

  I have an html document, and I want to pull the tables out of this document and return them as arrays. I'm picturing 2 functions, one that finds all the html tables in a document, and a second one that turns html tables into 2-dimensional arrays. Something like this: htmltables = get_tables(htmldocument) for table in htmltables: array=make_array(table) There's 2 catches: 1. The number tables varies day to day 2. The tables have all kinds of weird extra formatting, like bold and blink tags, randomly thrown in. Thanks!

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• GA written in Java

  - by EnderMB

  I am attempting to write a Genetic Algorithm based on techniques I had picked up from the book "AI Techniques for Game Programmers" that uses a binary encoding and fitness proportionate selection (also known as roulette wheel selection) on the genes of the population that are randomly generated within the program in a two-dimensional array. I recently came across a piece of pseudocode and have tried to implement it, but have come across some problems with the specifics of what I need to be doing. I've checked a number of books and some open-source code and am still struggling to progress. I understand that I have to get the sum of the total fitness of the population, pick a random number between the sum and zero, then if the number is greater than the parents to overwrite it, but I am struggling with the implementation of these ideas. Any help in the implementation of these ideas would be very much appreciated as my Java is rusty.

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• Most efficient way to save tile data of an isometric game

  - by Harmen

  Hello, I'm working on an isometric game for fast browsers that support <canvas>, which is great fun. To save information of each tile, I use a two-dimensional array which contains numbers representing a tile ID, like: var level = [[1, 1, 1, 2, 1, 0], [0, 1, 1, 2, 0, 1], [0, 1, 1, 2, 1, 1]]; var tiles = [ {name: 'grass', color: 'green'}, {name: 'water', color: 'blue'}, {name: 'forest', color: 'ForestGreen'} ]; So far it works great, but now I want to work with heights and slopes like in this picture: For each tile I need to save it's tile ID, height and information about which corners are turned upward. I came up with a simple idea about a bitwise representation of all four corners, like this: 1011 // top, bottom and left corner turned up My question is: what is the most efficient way to save these three values for each cell? Is it possible to save these three values as one integer?

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• Single dimension peak fitting

  - by bufferz

  I have a single dimensional array of floating point values (c# doubles FYI) and I need to find the "peak" of the values ... as if graphed. I can't just take the highest value, as the peak is actually a plateau that has small fluctuations. This plateau is in the middle of a bunch of noise. I'm looking find a solution that would give me the center of this plateau. An example array might look like this: 1,2,1,1,2,1,3,2,4,4,4,5,6,8,8,8,8,7,8,7,9,7,5,4,4,3,3,2,2,1,1,1,1,1,2,1,1,1,1 where the peak is somewhere in the bolded section. Any ideas?

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• design using a readonly class in c#

  - by edosoft

  Hi Small design question here. I'm trying to develop a calculation app in C#. I have a class, let's call it InputRecord, which holds 100s of fields (multi dimensional arrays) This InputRecordclass will be used in a number of CalculationEngines. Each CalculcationEngine can make changes to a number of fields in the InputRecord. These changes are steps needed for it's calculation. Now I don't want the local changes made to the InputRecord to be used in other CalculcationEngine's classes. The first solution that comes to mind is using a struct: these are value types. However I'd like to use inheritance: each CalculationEngine needs a few fields only relevant to that engine: it's has it's own InputRecord, based on BaseInputRecord. Can anyone point me to a design that will help me accomplish this?

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• JavaScript Array Problem

  - by JasonS

  Hi, This wasn't the question I was going to ask but I have unexpectedly run aground with JavaScript arrays. I come from a PHP background and after looking at a few websites I am none the wiser. I am trying to create a multi-dimensional array. var photos = new Array; var a = 0; $("#photos img").each(function(i) { photos[a]["url"] = this.src; photos[a]["caption"] = this.alt; photos[a]["background"] = this.css('background-color'); a++; }); Error message: photos[a] is undefined. How do I do this. Thanks.

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• Sorting data by relevance, from multiple tables

  - by Oden

  Hey, How is it possible to sort data from multiple tables by relevance? My table structure is following: I have 3 tables in my database, one table contains the name of solar systems, the second for e.g. of planets. There is one more table, witch is a connection between solar systems and planets. If I want to get data of a planet, witch is in the Milky Way, i post this data to the server, and it gives me a multi-dimensional array witch contains: The Milky Way, with every planet in it Every planet, witch name contains the string Milky Way (maybe thats a bat example because i don't think that theres but one planet with this name, but the main concept is on file) But, i want to set the most relevant restaurants to the top of the array. (for the relevance i would check the description of the restaurants or something like that) So, how would you do that kind of data sorting?

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• problem with hierarchical clustering in Python

  - by user248237

  I am doing a hierarchical clustering a 2 dimensional matrix by correlation distance metric (i.e. 1 - Pearson correlation). My code is the following (the data is in a variable called "data"): from hcluster import * Y = pdist(data, 'correlation') cluster_type = 'average' Z = linkage(Y, cluster_type) dendrogram(Z) The error I get is: ValueError: Linkage 'Z' contains negative distances. What causes this error? The matrix "data" that I use is simply: [[ 156.651968 2345.168618] [ 158.089968 2032.840106] [ 207.996413 2786.779081] [ 151.885804 2286.70533 ] [ 154.33665 1967.74431 ] [ 150.060182 1931.991169] [ 133.800787 1978.539644] [ 112.743217 1478.903191] [ 125.388905 1422.3247 ]] I don't see how pdist could ever produce negative numbers when taking 1 - pearson correlation. Any ideas on this? thank you.

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• Fast way to perform addition of 2 LARGE float arrays in Android. Optional JNI or Opengl ES

  - by nathan

  I simply need to add floatArray1 to floatArray2 storing the result in floatArray2.. no third array.. all arrays are one dimensional but are very large... probibly as large as the os will let me get away with. Max i would need is two float arrays with 40,000 floats each... but i could get away with 1/10th that i suppose minimum. Would love to do this in 1/30th or 1/60th of a second but that does not seem possible? Also if the code is JNI,NDK or OpenGL ES thats fine.. does android have an assembly language or like machine code i could use somehow?

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• MATLAB: draw centroids

  - by Myx

  Hello - my main question is given a feature centroid, how can I draw it in MATLAB? In more detail, I have an NxNx3 image (an rgb image) of which I take 4x4 blocks and compute a 6-dimensional feature vector for each block. I store these feature vectors in an Mx6 matrix on which I run kmeans function and obtain the centroids in a kx6 matrix, where k is the number of clusters and 6 is the number of features for each block. How can I draw these center clusters in my image in order to visualize if the algorithm is performing the way I wish it to perform? Or if anyone has any other way/suggestions on how I can visualize the centroids on my image, I'd greatly appreciate it. Thank you.

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• Plotting Points in Java with Interaction

  - by mellort

  I have a large number of data points which are two dimensional coordinates with non-integer values (floats). I am looking for a Java library that can help me plot these points, allowing for custom point size, color, and labels. Further, I would like the user to be able to interact with the points with panning and zooming, and I want to be able to capture KeyEvents from the user. Processing looks great for what I want, but I don't want to do everything from scratch. Is there a better solution? Thanks in advance.

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• routine to generate a 2d array from two 1d arrays and a function

  - by intuited

  I'm guessing that there's a word for this concept, and that it's available in at least some popular languages, but my perfunctory search was fruitless. A pseudocode example of what I'd like to do: function foo(a, b) { return a * b // EG } a = [ 1, 2, 3 ] b = [ 4, 5, 6 ] matrix = the_function_for_which_I_search(foo, [a, b] ) print matrix => [ [ 4, 8, 12], [5, 10, 15], [6, 12, 18] ] // or function concatenate(a,b) return a.b } print the_function_for_which_I_search( concatenate, [ a, b ]) => [ [ '14', '24', '34'], ['15', '25', '35'], [16', '26', '36'] ] In other words, function_for_which_I_search will apply the function given as its first argument to each combination of the elements of the two arrays passed as its second argument, and return the results as a two-dimensional array. I would like to know if such a routine has a common name, and if it's available in a python module, cpan package, ruby gem, pear package, etc. I'm also wondering if this is a core function in other languages, maybe haskell or R?

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• Distributing a function over a single dimension of an array in MATLAB?

  - by Alex Feinman

  I often find myself wanting to collapse an n-dimensional matrix across one dimension, and can't figure out if there is a concise incantation I can use to do this. For example, when parsing an image, I often want to do something like this. (Note! Illustrative example only. I know about rgb2gray for this specific case.) img = imread('whatever.jpg'); s = size(img); for i=1:s(1) for j=1:s(2) bw_img = mean(img(i,j,:)); end end I would love to express this as something like: bw = on(color, 3, @mean); or bw(:,:,1) = mean(color); Is there a short way to do this?

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• Is there a name for this type of algorithm?

  - by rehanift

  I have a 2 dimensional array forming a table: [color][number][shape ] ------------------------- [black][10 ][square ] [black][10 ][circle ] [red ][05 ][triangle] [red ][04 ][triangle] [green][11 ][oval ] and what I want to do is group largest common denominators, such that we get: 3 groups group #1: color=black, number=10, shapes = [square, circle] group #2: color=red, shape=triange, numbers = [05,04] group #3: color=green, number=11, shape = oval I wrote code that will handle a 2 "column" scenario, then I needed to adjusted it for 3 and I was figuring I might as well do it for n. I wanted to check first if there is some literature around this but I can't think of what to start looking for!

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• Why the difference in speed?

  - by AngryHacker

  Consider this code: function Foo(ds as OtherDLL.BaseObj) dim lngRowIndex as long dim lngColIndex as long for lngRowIndex = 1 to ubound(ds.Data, 2) for lngColIndex = 1 to ds.Columns.Count Debug.Print ds.Data(lngRowIndex, lngColIndex) next next end function OK, a little context. Parameter ds is of type OtherDLL.BaseObj which is defined in a referenced ActiveX DLL. ds.Data is a variant 2-dimensional array (one dimension carries the data, the other one carries the column index. ds.Columns is a Collection of columns in 'ds.Data`. Assuming there are at least 400 rows of data and 25 columns, this code takes about 15 seconds to run on my machine. Kind of unbelievable. However if I copy the variant array to a local variable, so: function Foo(ds as OtherDLL.BaseObj) dim lngRowIndex as long dim lngColIndex as long dim v as variant v = ds.Data for lngRowIndex = 1 to ubound(v, 2) for lngColIndex = 1 to ds.Columns.Count Debug.Print v(lngRowIndex, lngColIndex) next next end function the entire thing processes in barely any noticeable time (basically close to 0). Why?

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• C++ domain specific embedded language operators

  - by aaa

  hi. In numerical oriented languages (Matlab, Fortran) range operator and semantics is very handy when working with multidimensional data. For example: A(i:j,k,:n) // represents two-dimensional slice B(i:j,0:n) of A at index k unfortunately C++ does not have range operator (:). of course it can be emulated using range/slice functor, but semantics is less clean than Matlab. I am prototyping matrix/tensor domain language in C++ and am wondering if there any options to reproduce range operator. I still would like to rely on C++/prprocessor framework exclusively. So far I have looked through boost wave which might be an suitable option. is there any other means to introduce new operators to C++ DSL?

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• Visit neighbor of a position in a 2d-array

  - by Martin

  I have the following two dimensional array: static int[,] arr = new int[5, 5] { { 00, 00, 00, 01, 00 }, { 00, 00, 01, 01, 00 }, { 00, 00, 01, 01, 00 }, { 00, 00, 01, 01, 00 }, { 00, 00, 00, 01, 00 }, }; I have to a implement a method called Hit(int x, int y). When we hit a 0 in the array (i.e. Hit(0, 0), Hit(1, 1), but not Hit(3, 0)) I would like all the adjacent zeros to the zero we hit to be incremented by 10. So if I call Hit(1, 1), the array should become the following. static int[,] arr = new int[5, 5] { { 10, 10, 10, 01, 00 }, { 10, 10, 01, 01, 00 }, { 10, 10, 01, 01, 00 }, { 10, 10, 01, 01, 00 }, { 10, 10, 10, 01, 00 }, }; Any idea how I could implement that? It sounds to me like a Depth First Search/Recursive sort-of algorithm should do the job, but I haven't been able to implement it for an 2d array. Thanks for the help!

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• How to build up a lookup table in microcontroller?

  - by GiGi

  Hi, I am so confused about how to build up a 3-dimension lookup table. Is the template as follows: create a 3 dimensional array to store data. Then create linked list. Then create function 'insert' to put all the data into the array? As some book said, linked list should be static const, is it need to create another function to expand the list? Because the lookup table should be used in a microcontroller, it only needs to finish the operation of putting the data into the array and whenever want to find the data, it will be fast and easy to search. Could you help me with that and give me some suggestions? Thank you.

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• Trouble Copying custom class initialization

  - by Parad0x13

  I have a custom class of type NSObject that contains a single NSMutableArray. This class is called Mutable2DArray and is designed to emulate a 2 dimensional array of type NSMutableArray. There is a custom init method - (id)initWithX:(int)x Y:(int)y that asks for the dimensions for the array and allocates the required arrays within the only array the class owns. My issue is when I try to copy an instance of Mutable2DArray I get an error saying the copyWithZone is an unrecognized selector. I thought copy was a base method of NSObject so I'm confused why I cant create a copy of the instance like this: Mutable2DArray *Array1 = [[Mutable2DArray alloc] initWithX:10 Y:10]; Mutable2DArray *Array2 = [Array1 copy]; Am I missing something so obvious here?

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• CREATE Excel File with hyperlinks in PHP

  - by Brian

  I have the following method to create an Excel file from in PHP starting with a two-dimensional array: header("Content-Disposition: attachment; filename=ExcelFile.xls"); header("Content-Type: application/vnd.ms-excel"); $Data[] = array('field1', 'field2', 'field3'); $Data[] = array('field1', 'field2', 'field3'); $Data[] = array('field1', 'field2', 'field3'); foreach($Data as $key => $val) { echo implode("\t", array_values($val)) . "\n"; } Would it be possible to include a hyperlink to a webpage in this file?

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• Distance between hyperplanes

  - by michael dillard

  I'm trying to teach myself some machine learning, and have been using the MNIST database (http://yann.lecun.com/exdb/mnist/) do so. The author of that site wrote a paper in '98 on all different kinds of handwriting recognition techniques, available at http://yann.lecun.com/exdb/publis/pdf/lecun-98.pdf. The 10th method mentioned is a "Tangent Distance Classifier". The idea being that if you place each image in a (NxM)-dimensional vector space, you can compute the distance between two images as the distance between the hyperplanes formed by each where the hyperplane is given by taking the point, and rotating the image, rescaling the image, translating the image, etc. I can't figure out enough to fill in the missing details. I understand that most of these are indeed linear operators, so how does one use that fact to then create the hyperplane? And once we have a hyperplane, how do we take its distance with other hyperplanes?

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