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  • How to convert floats to human-readable fractions?

    - by Swaroop C H
    Let's say we have 0.33, we need to output "1/3". If we have "0.4", we need to output "2/5". The idea is to make it human-readable to make the user understand "x parts out of y" as a better way of understanding data. I know that percentages is a good substitute but I was wondering if there was a simple way to do this?

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  • SOM Algorithm Matlab HELP

    - by Tim
    I'm trying to pass a txt file to som_read_data from a GUI......i created a function that takes a txt file from the GUI and then passes it to som_read_data..but i'm getting some errors...here are a list of some of the errors.....any one with ideas? ??? Error using ==> ftell Invalid file identifier. Use fopen to generate a valid file identifier. Error in ==> som_read_data at 169 fpos1 = ftell(fid); c1 = 0; % read first non-comment line Error in ==> prog_som at 3 sD = som_read_data(m);

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  • String chunking algorithm with natural language context

    - by Chris Ballance
    I have a arbitrarily large string of text from the user that needs to be split into 10k chunks (potentially adjustable value) and sent off to another system for processing. Chunks cannot be longer than 10k (or other arbitrary value) Text should be broken with natural language context in mind split on punctuation when possible split on spaces if no punction exists break a word as a last resort I'm trying not to re-invent the wheel with this, any suggestions before I roll this from scratch? Using C#.

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  • naive bayesian spam filter question

    - by Microkernel
    Hi guys, I am planning to implement spam filter using Naive Bayesian classification model. Online I see a lot of info on Naive Bayesian classification, but the problem is its a lot of mathematical stuff, than clearly stating how its done. And the problem is I am more of a programmer than a mathematician (yes I had learnt Probability and Bayesian theorem back in school, but out of touch for a long long time, and I don't have luxury of learning it now (Have nearly 3 weeks to come-up with a working prototype)). So if someone can explain or point me to location where its explained for programmers than a mathematician, it would be a great help. PS: By the way I have to implement it in C, if you want to know. :( Regards, Microkernel

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  • Sparse matrices / arrays in Java

    - by DanM
    I'm working on a project, written in Java, which requires that I build a very large 2-D sparse array. Very sparse, if that makes a difference. Anyway: the most crucial aspect for this application is efficency in terms of time (assume loads of memory, though not nearly so unlimited as to allow me to use a standard 2-D array -- the key range is in the billions in both dimensions). Out of the kajillion cells in the array, there will be several hundred thousand cells which contain an object. I need to be able to modify cell contents VERY quickly. Anyway: Does anyone know a particularly good library for this purpose? It would have to be Berkeley, LGPL or similar license (no GPL, as the product can't be entirely open-sourced). Or if there's just a very simple way to make a homebrew sparse array object, that'd be fine too. I'm considering MTJ, but haven't heard any opinions on its quality. Thanks!! -Dan

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  • Skip List vs. Binary Tree

    - by Claudiu
    I recently came across the data structure known as a Skip list. They seem to have very similar behavior to a binary search tree... my question is - why would you ever want to use a skip list over a binary search tree?

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  • Optimizing Levenshtein Distance Algorithm

    - by Matt
    I have a stored procedure that uses Levenshtein Distance to determine the result closest to what the user typed. The only thing really affecting the speed is the function that calculates the Levenshtein Distance for all the records before selecting the record with the lowest distance (I've verified this by putting a 0 in place of the call to the Levenshtein function). The table has 1.5 million records, so even the slightest adjustment may shave off a few seconds. Right now the entire thing runs over 10 minutes. Here's the method I'm using: ALTER function dbo.Levenshtein ( @Source nvarchar(200), @Target nvarchar(200) ) RETURNS int AS BEGIN DECLARE @Source_len int, @Target_len int, @i int, @j int, @Source_char nchar, @Dist int, @Dist_temp int, @Distv0 varbinary(8000), @Distv1 varbinary(8000) SELECT @Source_len = LEN(@Source), @Target_len = LEN(@Target), @Distv1 = 0x0000, @j = 1, @i = 1, @Dist = 0 WHILE @j <= @Target_len BEGIN SELECT @Distv1 = @Distv1 + CAST(@j AS binary(2)), @j = @j + 1 END WHILE @i <= @Source_len BEGIN SELECT @Source_char = SUBSTRING(@Source, @i, 1), @Dist = @i, @Distv0 = CAST(@i AS binary(2)), @j = 1 WHILE @j <= @Target_len BEGIN SET @Dist = @Dist + 1 SET @Dist_temp = CAST(SUBSTRING(@Distv1, @j+@j-1, 2) AS int) + CASE WHEN @Source_char = SUBSTRING(@Target, @j, 1) THEN 0 ELSE 1 END IF @Dist > @Dist_temp BEGIN SET @Dist = @Dist_temp END SET @Dist_temp = CAST(SUBSTRING(@Distv1, @j+@j+1, 2) AS int)+1 IF @Dist > @Dist_temp SET @Dist = @Dist_temp BEGIN SELECT @Distv0 = @Distv0 + CAST(@Dist AS binary(2)), @j = @j + 1 END END SELECT @Distv1 = @Distv0, @i = @i + 1 END RETURN @Dist END Anyone have any ideas? Any input is appreciated. Thanks, Matt

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  • LinkedIn type friends connection required in php

    - by Akash
    Hi, I am creating a custom social network for one of my clients. In this I am storing the friends of a user in the form of CSV as shown below in the user table uid user_name friends 1 John 2 2 Jack 3,1 3 Gary 2,4 4 Joey 3 In the above scenario if the logged in user is John and if he visits the profile page of Joey, the connection between them should appear as John-Jack-Gary-Joey I am able to establish the connection at level 1 i.e If Jack visits Joey's profile I am able to establish the following : Jack-Gary-Joey But for the 2nd level I need to get into the same routine of for loops which I know is not the right solution + I am not able to implement that as well. So, can someone please help me with this? Thanks in Advance, Akash P:S I am not in a position to change the db architecture :(

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  • Time complexity of a sorting algorithm

    - by Passonate Learner
    The two programs below get n integers from file and calculates the sum of ath to bth integers q(number of question) times. I think the upper program has worse time complexity than the lower, but I'm having problems calculating the time complexity of these two algorithms. [input sample] 5 3 5 4 3 2 1 2 3 3 4 2 4 [output sample] 7 5 9 Program 1: #include <stdio.h> FILE *in=fopen("input.txt","r"); FILE *out=fopen("output.txt","w"); int n,q,a,b,sum; int data[1000]; int main() int i,j; fscanf(in,"%d%d",&n,&q); for(i=1;i<=n;i++) fscanf(in,"%d",&data[i]); for i=0;i<q;i++) { fscanf(in,"%d%d",&a,&b); sum=0; for(j=a;j<=b;j++) sum+=data[j]; fprintf(out,"%d\n",sum); } return 0; } Program 2: #include <stdio.h> FILE *in=fopen("input.txt","r"); FILE *out=fopen("output.txt","w"); int n,q,a,b; int data[1000]; int sum[1000]; int main() { int i,j; fscanf(in,"%d%d",&n,&q); for(i=1;i<=n;i++) fscanf(in,"%d",&data[i]); for(i=1;i<=n;i++) sum[i]=sum[i-1]+data[i]; for(i=0;i<q;i++) { fscanf(in,"%d%d",&a,&b); fprintf(out,"%d\n",sum[b]-sum[a-1]); } return 0; } The programs below gets n integers from 1 to m and sorts them. Again, I cannot calculate the time complexity. [input sample] 5 5 2 1 3 4 5 [output sample] 1 2 3 4 5 Program: #include <stdio.h> FILE *in=fopen("input.txt","r") FILE *out=fopen("output.txt","w") int n,m; int data[1000]; int count[1000]; int main() { int i,j; fscanf(in,"%d%d",&n,&m); for(i=0;i<n;i++) { fscanf(in,"%d",&data[i]); count[data[i]]++ } for(i=1;i<=m;i++) { for(j=0;j<count[i];j++) fprintf(out,"%d ",i); } return 0; } It's ironic(or not) that I cannot calculate the time complexity of my own algorithms, but I have passions to learn, so please programming gurus, help me!

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  • Floating point conversion from Fixed point algorithm

    - by Viks
    Hi, I have an application which is using 24 bit fixed point calculation.I am porting it to a hardware which does support floating point, so for speed optimization I need to convert all fixed point based calculation to floating point based calculation. For this code snippet, It is calculating mantissa for(i=0;i<8207;i++) { // Do n^8/7 calculation and store // it in mantissa and exponent, scaled to // fixed point precision. } So since this calculation, does convert an integer to mantissa and exponent scaled to fixed point precision(23 bit). When I tried converting it to float, by dividing the mantissa part by precision bits and subtracting the exponent part by precision bit, it really does' t work. Please help suggesting a better way of doing it.

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  • Convert latitude and longitude into northern and eastings

    - by Rippo
    Hi I have the following UK postcode dy8 3xt and know that the latitude and longitude is:- 52.190108 -2.517266 I also know that the Eastings, Northings for the postcode is:- 389490 283880 However I am struggling to find the equation that converts lat/long to northings and Eastings, I would prefer to have the equation in both in jScript and c# (I am being greedy)! Can anyone help?

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  • geofencing algorithm

    - by jose
    i have got a latitude and longitude of a point... i want to get all the readings of latitude and longitude with in a particular radius... is there any methods to calculate all laltitudes and longtiudes with in a radius with respect to a given point?...can u help me

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  • Using base64 encoding as a mechanism to detect changes

    - by Mikos
    Is it possible to detect changes in the base64 encoding of an object to detect the degree of changes in the object. Suppose I send a document attachment to several users and each makes changes to it and emails back to me, can I use the string distance between original base64 and the received base64s to detect which version has the most changes. Would that be a valid metric? If not, would there be any other metrics to quantify the deltas?

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  • Genetic Algorithms applied to Curve Fitting

    - by devoured elysium
    Let's imagine I have an unknown function that I want to approximate via Genetic Algorithms. For this case, I'll assume it is y = 2x. I'd have a DNA composed of 5 elements, one y for each x, from x = 0 to x = 4, in which, after a lot of trials and computation and I'd arrive near something of the form: best_adn = [ 0, 2, 4, 6, 8 ] Keep in mind I don't know beforehand if it is a linear function, a polynomial or something way more ugly, Also, my goal is not to infer from the best_adn what is the type of function, I just want those points, so I can use them later. This was just an example problem. In my case, instead of having only 5 points in the DNA, I have something like 50 or 100. What is the best approach with GA to find the best set of points? Generating a population of 100, discard the worse 20% Recombine the remaining 80%? How? Cutting them at a random point and then putting together the first part of ADN of the father with the second part of ADN of the mother? Mutation, how should I define in this kind of problem mutation? Is it worth using Elitism? Any other simple idea worth using around? Thanks

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  • Algorithm for finding a rectangle constrained to its parent

    - by Milo
    Basically what I want to do is illustrated here: I start with A and B, then B is conformed to A to create C. The idea is, given TLBR rectangles A, B, make C I also need to know if it produces an empty rectangle (B outside of A case). I tried this but it just isn't doing what I want: if(clipRect.getLeft() > rect.getLeft()) L = clipRect.getLeft(); else L = rect.getLeft(); if(clipRect.getRight() < rect.getRight()) R = clipRect.getRight(); else R = rect.getRight(); if(clipRect.getBottom() > rect.getBottom()) B = clipRect.getBottom(); else B = rect.getBottom(); if(clipRect.getTop() < rect.getTop()) T = clipRect.getTop(); else T = rect.getTop(); if(L < R && B < T) { clipRect = AguiRectangle(0,0,0,0); } else { clipRect = AguiRectangle::fromTLBR(T,L,B,R); } Thanks

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  • Most efficient way of creating tree from adjacency list

    - by Jeff Meatball Yang
    I have an adjacency list of objects (rows loaded from SQL database with the key and it's parent key) that I need to use to build an unordered tree. It's guaranteed to not have cycles. This is taking wayyy too long (processed only ~3K out of 870K nodes in about 5 minutes). Running on my workstation Core 2 Duo with plenty of RAM. Any ideas on how to make this faster? public class StampHierarchy { private StampNode _root; private SortedList<int, StampNode> _keyNodeIndex; // takes a list of nodes and builds a tree // starting at _root private void BuildHierarchy(List<StampNode> nodes) { Stack<StampNode> processor = new Stack<StampNode>(); _keyNodeIndex = new SortedList<int, StampNode>(nodes.Count); // find the root _root = nodes.Find(n => n.Parent == 0); // find children... processor.Push(_root); while (processor.Count != 0) { StampNode current = processor.Pop(); // keep a direct link to the node via the key _keyNodeIndex.Add(current.Key, current); // add children current.Children.AddRange(nodes.Where(n => n.Parent == current.Key)); // queue the children foreach (StampNode child in current.Children) { processor.Push(child); nodes.Remove(child); // thought this might help the Where above } } } } public class StampNode { // properties: int Key, int Parent, string Name, List<StampNode> Children }

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  • Invert a stack, without using extra data structures?

    - by vks
    How would you invert a stack, without using extra data structures, like a second, or temporary, stack. Thus no stack1-stack2 or stack-queue-stack implementation in the answer. You just have access to push/pop feature of a standard stack. I think there is way to do it by keeping a global counter and using pointer manipulation. If I solve it myself, I will post it. If someone else figures it out, please post your solution.

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  • Implementing PageRank using MapReduce

    - by Nick D.
    Hello, I'm trying to get my head around an issue with the theory of implementing the PageRank with MapReduce. I have the following simple scenario with three nodes: A B C. The adjacency matrix is here: A { B, C } B { A } The PageRank for B for example is equal to: (1-d)/N + d ( PR(A) / C(A) ) N = number of incoming links to B PR(A) = PageRank of incoming link A C(A) = number of outgoing links from page A I am fine with all the schematics and how the mapper and reducer would work but I cannot get my head around how at the time of calculation by the reducer, C(A) would be known. How will the reducer, when calculating the PageRank of B by aggregating the incoming links to B will know the number of outgoing links from each page. Does this require a lookup in some external data source?

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  • Average function without overflow exception

    - by Ron Klein
    .NET Framework 3.5. I'm trying to calculate the average of some pretty large numbers. For instance: using System; using System.Linq; class Program { static void Main(string[] args) { var items = new long[] { long.MinValue + 100, long.MinValue + 200, long.MinValue + 300 }; try { var avg = items.Average(); Console.WriteLine(avg); } catch (OverflowException ex) { Console.WriteLine("can't calculate that!"); } Console.ReadLine(); } } Obviously, the mathematical result is 9223372036854775607 (long.MaxValue - 200), but I get an exception there. This is because the implementation (on my machine) to the Average extension method, as inspected by .NET Reflector is: public static double Average(this IEnumerable<long> source) { if (source == null) { throw Error.ArgumentNull("source"); } long num = 0L; long num2 = 0L; foreach (long num3 in source) { num += num3; num2 += 1L; } if (num2 <= 0L) { throw Error.NoElements(); } return (((double) num) / ((double) num2)); } I know I can use a BigInt library (yes, I know that it is included in .NET Framework 4.0, but I'm tied to 3.5). But I still wonder if there's a pretty straight forward implementation of calculating the average of integers without an external library. Do you happen to know about such implementation? Thanks!! UPDATE: The previous example, of three large integers, was just an example to illustrate the overflow issue. The question is about calculating an average of any set of numbers which might sum to a large number that exceeds the type's max value. Sorry about this confusion. I also changed the question's title to avoid additional confusion. Thanks all!!

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  • 3 dimensional bin packing algorithms

    - by BuschnicK
    I'm faced with a 3 dimensional bin packing problem and am currently conducting some preliminary research as to which algorithms/heuristics are currently yielding the best results. Since the problem is NP hard I do not expect to find the optimal solution in every case, but I was wondering: 1) what are the best exact solvers? Branch and Bound? What problem instance sizes can I expect to solve with reasonable computing resources? 2) what are the best heuristic solvers? 3) What off-the-shelf solutions exist to conduct some experiments with?

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  • Visualization of Nelder-Mead algorithm in gnuplot

    - by gorczas
    Hi, does anyone know how I can achieve drawing triangle on level sets of some 3d function (something like on this image in gnuplot? When I tried doing this after reading some tutorials: gnuplot> set border 15 front linetype -1 linewidth 1.000 gnuplot> set logscale z 10 gnuplot> set view map gnuplot> set isosamples 60, 60 gnuplot> unset surface gnuplot> set contour base gnuplot> unset clabel gnuplot> set style data lines gnuplot> set ticslevel 0 gnuplot> set noztics gnuplot> set title "Trwa symulacja" gnuplot> set xlabel "x" gnuplot> set xrange [ * : * ] noreverse nowriteback gnuplot> set ylabel "y" gnuplot> set zlabel "" gnuplot> set yrange [ * : * ] noreverse nowriteback gnuplot> set zrange [ * : * ] noreverse nowriteback gnuplot> splot [-10.5:10.5] [-10.5:10.5] x**2 +y**2 with lines lc rgb "#000000" notitle,\ >'-' with lines notitle input data ('e' ends) > 5.39703780733842 0.424994542694183 29.3086374551602 input data ('e' ends) > -4.80045950473308 -8.66307635892326 98.0933034571172 input data ('e' ends) > -3.56740563691939 3.31903046267993 23.7423461905216 input data ('e' ends) > 5.39703780733842 0.424994542694183 29.3086374551602 input data ('e' ends) > e But I'm still getting warning: "Cannot contour non grid data. Please use "set dgrid3d".".

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