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  • What is the most efficient way to determine if a directed graph is singly connected?

    - by zebraman
    I am working on an assignment where one of the problems asks to derive an algorithm to check if a directed graph G=(V,E) is singly connected (there is at most one simple path from u to v for all distinct vertices u,v of V. Of course you can brute force check it, which is what I'm doing right now, but I want to know if there's a more efficient way. Could anyone point me in the right direction?

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  • How to plot 3D graphs in Excel from CSV data?

    - by Primx
    I have data formatted like this in a csv file: a, 1, 4, 6.0 a, 2, 42, 16.0 a, 5, 14, 69.3 a, 11, 4, 7.0 b, 1, 45, 6.0 b, 2, 45, 1.9 b, 9, 2, 4.4 b, 11, 4, 7.9 lines with first parameter a is one set of data, and first parameter b represents another set. My aim is to plot two lines on the same graph, one with points (1, 4, 6.0), (2, 42, 16.0), (5, 14, 69.3), (11, 4, 7.0) and the other with points (1, 45, 6.0), (2, 45, 1.9), (9, 2, 4.4), (11, 4, 7.9) I am able to import the data directly in MS Excel, but am not sure how to plot them. How can I plot this data?

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  • Need help starting with DSL for charts/graphs

    - by Rex M
    I am unaware of any established work into Domain Specific Languages for describing charts / graphs. I am looking for specific answers of "yes, something like that exists (here)". To help be clear, in case I am possibly using the wrong verbiage to describe it, to me a DSL for charts would most certainly include: A grammar for describing the shape of an expected data set A grammar for describing a pipeline of behaviors that render an output Abstract / high-level enough to be mappable to most tool-specific grammars, such as Excel, Highchart, matplotlib, etc.

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  • When can I be sure a directed graph is acyclic?

    - by Daniel Scocco
    The definition for directed acyclic graph is this: "there is no way to start at some vertex v and follow a sequence of edges that eventually loops back to v again." So far so good, but I am trying to find some premises that will be simpler to test and that will also guarantee the graph is acyclic. I came up with those premises, but they are pretty basic so I am sure other people figured it out in the past (or they are incorrect). The problem is I couldn't find anything related on books/online, hence why I decided to post this question. Premise 1: If all vertices of the graph have an incoming edge, then the graph can't be acyclic. Is this correct? Premise 2: Assume the graph in question does have one vertex with no incoming edges. In this case, in order to have a cycle, at least one of the other vertices would need to have two or more incoming edges. Is this correct?

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  • What are graphs in laymen's terms

    - by Justin984
    What are graphs, in computer science, and what are they used for? In laymen's terms preferably. I have read the definition on Wikipedia: In computer science, a graph is an abstract data type that is meant to implement the graph and hypergraph concepts from mathematics. A graph data structure consists of a finite (and possibly mutable) set of ordered pairs, called edges or arcs, of certain entities called nodes or vertices. As in mathematics, an edge (x,y) is said to point or go from x to y. The nodes may be part of the graph structure, or may be external entities represented by integer indices or references. but I'm looking for a less formal, easier to understand definition.

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  • Git dirctet acyclic graph - children know their parents but not the other way around

    - by dayscott
    Git is implemented as a directed acyclic graph. Children know their parents but not the other way round. This makes sense because i can reach every commit only through a branch or a tag ( generally speaking through a reference). That's how i traverse the tree. What other reasons had the developers of Git to make "the children know their parents but not the other way around"?/ What are the key benefits of this?

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  • Can anyone give me tips how to solve this using Graphs in C or Java?

    - by peiska
    Can anyone give me tips how to solve this using Graphs in C or Java? I have a rectangular sector, that I have to escape, and I have energy that goes disappear every step that i give in the area. I have to give the only one possible solution, the one that uses the least number of steps. If there are at least two sectors with the same number of steps (X1, Y1) and (X2, Y2) then choose the first if X1 < X2 or if X1 = X2 and Y1 < Y2. the position( 1,1) corresponds to the upper left corner. Examples: This is one sector,and i start with 40 of energy and in the position (3,3) 12 11 12 11 3 12 12 12 11 11 12 2 1 13 11 11 12 2 13 2 14 10 11 13 3 2 1 12 10 11 13 13 11 12 13 12 12 11 13 11 13 12 13 12 12 11 11 11 11 13 13 10 10 13 11 12 the best solution to exit the sector is the position (5, 1) the remain energy is 12 and i need 8 steeps to leave the area. for this sector i start with 8 of energy and in the position (3,4). 4 3 3 2 2 3 2 2 5 2 2 2 3 3 2 1 2 2 3 2 2 4 3 3 2 2 4 1 3 1 4 3 2 3 1 2 2 3 3 0 3 4 And for this one there is no way out, cause it looses all the energy.

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  • Using Oracle ADF Data Visualization Tools (DVT) Line Graphs to Display Weather Information

    - by Christian David Straub
    OverviewA guest post by Jeanne Waldman.I have a simple JDeveloper Fusion application that retrieves weather data. I wanted to compare the week's temperatures of different locations in a graph. I decided to check out the dvt:lineGraph component, and it took me a few minutes to add it to my jspx page and supply it with data.Drag and Drop the dvt:lineGraph onto your pageI opened my .jspx page in design modeIn the Component Palette, I selected ADF Data Visualization.Then I dragged 'Line' onto my page.A dialog popped up giving me options of the type of line graph. I chose the default.A lineGraph displayed with some default data. Hook up your weather dataNow I wanted to hook up my own data. I browsed the tagdoc, and I found the tabularData attribute.Attribute: tabularDataType: java.util.ListTagDoc:Specifies a list of data that the graph uses to create a grid and populate itself. The List consists of a three-member Object array for each data value to be passed to the graph. The members of each array must be organized as follows: The first member (index 0) is the column label, in the grid, of the data value. This is generally a String. If the graph has a time axis, then this should be a Java Date. Column labels typically identify groups in the graph. The second member (index 1) is the row label, in the grid, of the data value. This is generally a String. Row labels appear as series labels in the graph (usually in the legend). The third member (index 2) is the data value, which is usually a Double.The first member is the column label of the data value. This would be the day of the week.The second member is the row label of the data value. This would be the location name.The third member is the data value, usually a Double. This would be the temperature. I already had all this information, I just needed to put it in a List with a three-member Object array for each data value.   /**    * This is used for the lineGraph to show the data for each location.    */   public List<Object[]> getTabularData()   {      List<Object[]> tabularData = new ArrayList<Object []>();      List<WeatherForecast> weatherForecastList = getWeatherForecastList();      // loop through the list and build up the tabular data. Then cache it.      for(WeatherForecast wf : weatherForecastList)      {        List<ForecastDay> forecastDayList = wf.getForecastDayList();        String location = wf.getLocation();        for (ForecastDay fday : forecastDayList)        {          String day = fday.getPrettyDate();          String highTemp = fday.getHighF();          tabularData.add(new Object[]{day, location, Double.valueOf(highTemp)});        }             }      return tabularData;    }  Now I bound the lineGraph to this method by setting tabularData to#{weatherForAllLocationsBean.tabularData}weatherForAllLocationsBean is my bean that is defined in faces-config.xml. Adding a barGraphIn about 30 seconds, I added a barGraph with the same data. I dragged and dropped a bar graph onto the page, used the same tabularData as I did in the line graph. The page looks like this:  ConclusionI was very happy how fast it was to hook up my weather data to these graphs. They look great, and they have built in functionality. For instance, I can hide/show a location by clicking on the name of the location in the legend.

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  • Shortest acyclic path on directed cyclic graph with negative weights/cycles

    - by Janathan
    I have a directed graph which has cycles. All edges are weighted, and the weights can be negative. There can be negative cycles. I want to find a path from s to t, which minimizes the total weight on the path. Sure, it can go to negative infinity when negative cycles exist. But what if I disallow cycles in the path (not in the original graph)? That is, once the path leaves a node, it can not enter the node again. This surely avoids the negative infinity problem, but surprisingly no known algorithm is found by a search on Google. The closest is Floyd–Warshall algorithm, but it does not allow negative cycles. Thanks a lot in advance. Edit: I may have generalized my original problem too much. Indeed, I am given a cyclic directed graph with nonnegative edge weights. But in addition, each node has a positive reward too. I want to find a simple path which minimizes (sum of edge weights on the path) - (sum of node rewards covered by the path). This can be surely converted to the question that I posted, but some structure is lost. And some hint from submodular analysis suggests this motivating problem is not NP-hard. Thanks a lot

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  • How do I make matlab legends match the colour of the graphs?

    - by Alex Gosselin
    Here is the code I used: x = linspace(0,2); e = exp(1); lin = e; quad = e-e.*x.*x/2; cub = e-e.*x.*x/2; quart = e-e.*x.*x/2+e.*x.*x.*x.*x/24; act = e.^cos(x); mplot = plot(x,act,x,lin,x,quad,x,cub,x,quart); legend('actual','linear','quadratic','cubic','quartic') This produces a legend matching the right colors to actual and linear, then after that it seems to skip over red on the graph, but not on the legend, i.e. the legend says quadratic should be red, but the graph shows it as green, the legend says cubic should be green, but the graph shows it as purple etc. Any help is appreciated.

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  • Drawing Directed Acyclic Graphs: Minimizing edge crossing?

    - by Robert Fraser
    Laying out the verticies in a DAG in a tree form (i.e. verticies with no in-edges on top, verticies dependent only on those on the next level, etc.) is rather simple without graph drawing algorithms such as Efficient Sugimiya. However, is there a simple algorithm to do this that minimizes edge crossing? (For some graphs, it may be impossible to completely eliminate edge crossing.) A picture says a thousand words, so is there an algorithm that would suggest: instead of: EDIT: As the picture suggests, a vertex's inputs are always on top and outputs are always below, which is another barrier to just pasting in an existing layout algorithm.

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  • How do I implement graphs and graph algorithms in a functional programming language?

    - by brad
    Basically, I know how to create graph data structures and use Dijkstra's algorithm in programming languages where side effects are allowed. Typically, graph algorithms use a structure to mark certain nodes as 'visited', but this has side effects, which I'm trying to avoid. I can think of one way to implement this in a functional language, but it basically requires passing around large amounts of state to different functions, and I'm wondering if there is a more space-efficient solution.

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  • Designing binary operations(AND, OR, NOT) in graphs DB's like neo4j

    - by Nicholas
    I'm trying to create a recipe website using a graph database, specifically neo4j using spring-data-neo4j, to try and see what can be done in Graph Databases. My model so far is: (Chef)-[HAS_INGREDIENT]->(Ingredient) (Chef)-[HAS_VALUE]->(Value) (Ingredient)-[HAS_INGREDIENT_VALUE]->(Value) (Recipe)-[REQUIRES_INGREDIENT]->(Ingredient) (Recipe)-[REQUIRES_VALUE]->(Value) I have this set up so I can do things like have the "chef" enter ingredients they have on hand, and suggest recipes, as well as suggest recipes that are close matches, but missing one ingredient. Some recipes can get complex, utilizing AND, OR, and NOT type logic, something like (Milk AND (Butter OR spread OR (vegetable oil OR olive oil))) and I'm wondering if it would be sane to model this in a graph using a tree type representation? An example of what I was thinking is to create three "node" types of AND, OR, and NOT and have each of them connect to the nodes value underneath. How else might this be represented in a Graph Database or is my example above a decent representation?

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  • Sentence Tree v/s Words List

    - by Rohit Jose
    I was recently tasked with building a Name Entity Recognizer as part of a project. The objective was to parse a given sentence and come up with all the possible combinations of the entities. One approach that was suggested was to keep a lookup table for all the know connector words like articles and conjunctions, remove them from the words list after splitting the sentence on the basis of the spaces. This would leave out the Name Entities in the sentence. A lookup is then done for these identified entities on another lookup table that associates them to the entity type, for example if the sentence was: Remember the Titans was a movie directed by Boaz Yakin, the possible outputs would be: {Remember the Titans,Movie} was {a movie,Movie} directed by {Boaz Yakin,director} {Remember the Titans,Movie} was a movie directed by Boaz Yakin {Remember the Titans,Movie} was {a movie,Movie} directed by Boaz Yakin {Remember the Titans,Movie} was a movie directed by {Boaz Yakin,director} Remember the Titans was {a movie,Movie} directed by Boaz Yakin Remember the Titans was {a movie,Movie} directed by {Boaz Yakin,director} Remember the Titans was a movie directed by {Boaz Yakin,director} Remember the {the titans,Movie,Sports Team} was {a movie,Movie} directed by {Boaz Yakin,director} Remember the {the titans,Movie,Sports Team} was a movie directed by Boaz Yakin Remember the {the titans,Movie,Sports Team} was {a movie,Movie} directed by Boaz Yakin Remember the {the titans,Movie,Sports Team} was a movie directed by {Boaz Yakin,director} The entity lookup table here would contain the following data: Remember the Titans=Movie a movie=Movie Boaz Yakin=director the Titans=Movie the Titans=Sports Team Another alternative logic that was put forward was to build a crude sentence tree that would contain the connector words in the lookup table as parent nodes and do a lookup in the entity table for the leaf node that might contain the entities. The tree that was built for the sentence above would be: The question I am faced with is the benefits of the two approaches, should I be going for the tree approach to represent the sentence parsing, since it provides a more semantic structure? Is there a better approach I should be going for solving it?

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  • Matrix multiplication - Scene Graphs

    - by bgarate
    I wrote a MatrixStack class in C# to use in a SceneGraph. So, to get the world matrix for an object I am suposed to use: WorldMatrix = ParentWorld * LocalTransform But, in fact, it only works as expected when I do the other way: WorldMatrix = LocalTransform * ParentWorld Mi code is: public class MatrixStack { Stack<Matrix> stack = new Stack<Matrix>(); Matrix result = Matrix.Identity; public void PushMatrix(Matrix matrix) { stack.Push(matrix); result = matrix * result; } public Matrix PopMatrix() { result = Matrix.Invert(stack.Peek()) * result; return stack.Pop(); } public Matrix Result { get { return result; } } public void Clear() { stack.Clear(); result = Matrix.Identity; } } Why it works this way and not the other? Thanks!

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  • GNU Octave - question about graphs and plotting

    - by Twórca
    I've had task to do - to make an graphical interpretation of adding two functions together: sin(8x) and multiplied -sign(x) in Octave, as shown on image above. And I've done that, but I don't know how to get rid of these lines, which link up gaps between separated values (for example, -1 and 1). I don't want them to be seen especially in third graph. To make helping me easier, I'm going to tell you what I did: I made linear series of numbers, from -100 to 99 (tempx). tempy = -sign(tempx) y1 = [tempy tempy tempy tempy] (this line is kinda funny, if you know Polish language) Creating y2 - sinus function y3 = y2 + y1 Plotting, subplotting... Screenshot Awaiting for instructions...

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  • Using Crystal Reports and ASP.NET to Create Drill through Reports and Graphs

    In this article, Vince examines the creation of an ASP.NET web application that uses the CrystalReportPartsViewer Control to create a drill through report where the user can view summary level data and click on a hyperlink to drill into the details.Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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