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• Comparing (similar) images with Python/PIL

  - by Attila Oláh

  I'm trying to calculate the similarity (read: Levenshtein distance) of two images, using Python 2.6 and PIL. I plan to use the python-levenshtein library for fast comparison. Main question: What is a good strategy for comparing images? My idea is something like: Convert to RGB (transparent - white) (or maybe convert to monochrome?) Scale up the smaller one to the larger one's size Convert each channel (= the only channel, if converted to monochrome) to a sequence (item value = color value of the pixel) Calculate the Levenshtein distance between the two sequences Of course, this will not handle cases like mirrored images, cropped images, etc. But for basic comparison, this should be useful. Is there a better strategy documented somewhere?

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• Objective C / iPhone comparing 2 CLLocations /GPS coordinates help

  - by user289503

  Ok , so thanks to Claus Broch I made some progress with comparing two GPS locations. I need to be able to say "IF currentlocation IS EQUAL TO (any GPS position from a list ) THEN do something My code at the moment is : CLLocationCoordinate2D bonusOne; bonusOne.latitude = 37.331689; bonusOne.longitude = -122.030731; Which is the simulators GPS location at Infinite Loop CLLocation *loc1 = [[CLLocation alloc] initWithLatitude:bonusOne.latitude longitude:bonusOne.longitude]; double distance = [loc1 getDistanceFrom:newLocation]; if(distance <= 10000000) { Then do something } Any number under 10000000 and it assumes that there is no match. Any ideas ? Thanks is advance.

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• getting `distance` of scroll

  - by Phil Jackson

  Hi, usinf javascript is it possible to work out the distance, or how far in pixels a window has been scrolled down? Regards Phil

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• Question on multi-probe Local Sensitive Hashing

  - by Yijinsei

  Hey guys sorry to be asking this kind noob question, but because I really need some guidance on how to use Multi probe LSH pretty urgently, so I did not do much research myself. I realize there is a lib call LSHKIT available that implemented that algorithm, but I have trouble trying to figure out how to use it. Right now, I have a few thousand feature vector 296 dimension, each representing an image. The vector is used to query an user input image, to retrieve the most similar image. The method I used to derive the distance between vector is euclidean distance. I know this might be a rather noob question, but do you guys have knowledge on how should i implement multi probe LSH? I am really very grateful to any answer or response.

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• Closest Approach question for math/physics heads

  - by Kyle

  I'm using a Segment to Segment closest approach method which will output the closest distance between two segments of length. These objects are moving at variable speed each, so even when it succeeds I'm currently using a 10-step method and calculating the distance between 2 spheres as they move along the two segments. So, basically the length of each segment is the object's traverse in the physics step, and the radius is the objects radius. By stepping, I can tell where they collide, and if they collide (Sort of; for the MOST part.).. I get the feeling that there could be something better. While I sort of believe that the first closest approach call is required, I think that the method immediately following it is a TAD weak. Can anyone help me out? I can illustrate this if needed. Thanks alot!

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• Trilateration using 3 latitude and longitude points, and 3 distances

  - by nohat

  There exists an unknown target location (latitude and longitude co-ordinates). I have 3 latitude and longitude co-ordinate pairs and for each pair a distance in kilometers to the target location. How can I calculate the co-ordinates of the target location? For example, say I have the following data points 37.418436,-121.963477 0.265710701754km 37.417243,-121.961889 0.234592423446km 37.418692,-121.960194 0.0548954278262km What I'd like is what would the guts of the function that takes that as input and returns 37.417959,-121.961954 as output look like? I understand how to calculate the distance between two points, from http://www.movable-type.co.uk/scripts/latlong.html I understand the general principle that with three circles you get exactly one point of overlap. What I'm hazy on is the math needed to calculate that point with this input.

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• C: sprintf and recursion

  - by Shinka

  In C, is it possible to use recursion within the sprintf function ? For some reason I get a segmentation fault when I do it: inline char *TreeNode_toString(const TreeNode *node) { char *out; if(TreeNode_isExternal(node)) // If the node has no children... { sprintf(out, "%s:%.2f", node->name, node->distance); } else // The node is strictly binary, so it will have two non-null children { char *l = TreeNode_toString(node->l); // l = left child char *r = TreeNode_toString(node->r); // r = right child sprintf(out, "(%s,%s):%.2f", l, r, node->distance); } return out; }

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• agent-based simulation: performance issue: Python vs NetLogo & Repast

  - by max

  I'm replicating a small piece of Sugarscape agent simulation model in Python 3. I found the performance of my code is ~3 times slower than that of NetLogo. Is it likely the problem with my code, or can it be the inherent limitation of Python? Obviously, this is just a fragment of the code, but that's where Python spends two-thirds of the run-time. I hope if I wrote something really inefficient it might show up in this fragment: UP = (0, -1) RIGHT = (1, 0) DOWN = (0, 1) LEFT = (-1, 0) all_directions = [UP, DOWN, RIGHT, LEFT] # point is just a tuple (x, y) def look_around(self): max_sugar_point = self.point max_sugar = self.world.sugar_map[self.point].level min_range = 0 random.shuffle(self.all_directions) for r in range(1, self.vision+1): for d in self.all_directions: p = ((self.point[0] + r * d[0]) % self.world.surface.length, (self.point[1] + r * d[1]) % self.world.surface.height) if self.world.occupied(p): # checks if p is in a lookup table (dict) continue if self.world.sugar_map[p].level > max_sugar: max_sugar = self.world.sugar_map[p].level max_sugar_point = p if max_sugar_point is not self.point: self.move(max_sugar_point) Roughly equivalent code in NetLogo (this fragment does a bit more than the Python function above): ; -- The SugarScape growth and motion procedures. -- to M ; Motion rule (page 25) locals [ps p v d] set ps (patches at-points neighborhood) with [count turtles-here = 0] if (count ps > 0) [ set v psugar-of max-one-of ps [psugar] ; v is max sugar w/in vision set ps ps with [psugar = v] ; ps is legal sites w/ v sugar set d distance min-one-of ps [distance myself] ; d is min dist from me to ps agents set p random-one-of ps with [distance myself = d] ; p is one of the min dist patches if (psugar >= v and includeMyPatch?) [set p patch-here] setxy pxcor-of p pycor-of p ; jump to p set sugar sugar + psugar-of p ; consume its sugar ask p [setpsugar 0] ; .. setting its sugar to 0 ] set sugar sugar - metabolism ; eat sugar (metabolism) set age age + 1 end On my computer, the Python code takes 15.5 sec to run 1000 steps; on the same laptop, the NetLogo simulation running in Java inside the browser finishes 1000 steps in less than 6 sec. EDIT: Just checked Repast, using Java implementation. And it's also about the same as NetLogo at 5.4 sec. Recent comparisons between Java and Python suggest no advantage to Java, so I guess it's just my code that's to blame? EDIT: I understand MASON is supposed to be even faster than Repast, and yet it still runs Java in the end.

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• HTTP Digest Authentication Fails With URL Parameters (CakePHP)

  - by NathanGaskin

  I have a RESTful API set up and working with CakePHP using mapResources() and parseExtensions(). Authentication is handled by CakePHP's security component using HTTP Digest Authentication. Everything works fine, unless I add parameters to the url, in the form: http://example.com/locations.xml?distance=4 Which causes the authentication to always fail. Any ideas? Edit: This seems to be an issue with the regex in parseDigestAuthData(). There's a semi-fix here: http://old.nabble.com/paginator-conflicts-with-Security-%3ErequireLogin---td16301573.html which now allows me to use the format: http://example.com/locations/index/distance:4/.xml But that's not RESTful and doesn't look all that pretty. Still, getting closer!

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• Finding coordinates of a point between two points?

  - by Nicros

  Doing some 3D stuff in wpf- want to use a simpler test to see if everything is working (before moving to curves). The basic question is given two points x1,y1,z1 and x2,y2,z2 I have calculated the distance between the points. But how to find the coordinates of another point (x3,y3,z3) that lies on that line at some distance? I.e. if my line is 100 long between -50,0,0 and 50,0,0 what are the coordinates of the point at 100 * 0.1 along the line? I think this is a simple formula but I haven't found it yet....

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• Python KMeans clustering words

  - by sadawd

  Dear Everyone I am interested to perform kmeans clustering on a list of words with the distance measure being Leveshtein. 1) I know there are a lot of frameworks out there, including scipy and orange that has a kmeans implementation. However they all require some sort of vector as the data which doesn't really fit me. 2) I need a good clustering implementation. I looked at python-clustering and realize that it doesn't a) return the sum of all the distance to each centroid, and b) it doesn't have any sort of iteration limit or cut off which ensures the quality of the clustering. python-clustering and the clustering algorithm on daniweb doesn't really work for me. Can someone find me a good lib? Google hasn't been my friend

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• mysql birthday reminder, leap year

  - by moodh

  Hi, I'm trying to sort out a result set that gives the 5 closest users sorted by upcoming birthday. This works perfectly until leap years comes into play. For example: May 15th - 96 days left May 15th - 97 days left The top result is a birth at 1987 and the lower is from 1988. u_birth is stored as yyyy-mm-dd. Is there a simple way to sort this problem without having to rewrite the entire query? SELECT u_birth, IF( DAYOFYEAR( u_birth ) >= DAYOFYEAR( NOW() ), DAYOFYEAR( u_birth ) - DAYOFYEAR( NOW() ), DAYOFYEAR( u_birth ) - DAYOFYEAR( NOW() ) + DAYOFYEAR( CONCAT( YEAR( NOW() ), '-12-31' ) ) ) AS distance FROM (blog_users) WHERE `s_agehide` = 0 ORDER BY distance ASC LIMIT 5 This query is taken and modified from the mysql manual: http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html#c7489

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• Adding an overlay to Google maps with path taken

  - by user341652

  Hi, I am trying to write a class to track a person's location(s), and to draw the path they've taken on a MapView. This feature of the program is for the user to track their speed, distance, path, etc. while running/cycling (or whatever else) using their Android phone. This is my first Android application, and I am not sure how to do the Overlay object for the MapView. I also wanted to see if anyone had opinions on the GPS-Tracking part I have written (if it would work, if there is a better way of doing it, code examples would be helpful). I currently have this for my GPSTrackerService: package org.drexel.itrain.logic; import java.util.Vector; import org.drexel.itrain.Constants; import android.app.Notification; import android.app.NotificationManager; import android.app.Service; import android.content.Context; import android.content.Intent; import android.content.SharedPreferences; import android.location.GpsSatellite; import android.location.GpsStatus; import android.location.Location; import android.location.LocationListener; import android.location.LocationManager; import android.location.GpsStatus.Listener; import android.os.Binder; import android.os.Bundle; import android.os.IBinder; import android.preference.PreferenceManager; public class GPSTrackingService extends Service { private static final int MAX_REASONABLE_SPEED = 60; private static final String TAG = "OGT.TrackingService"; private Context mContext; private LocationManager mLocationManager; private NotificationManager mNotificationManager; private Notification mNotification; private int mSatellites = 0; private int mTrackingState = Constants.GPS_TRACKING_UNKNOWN; private float mCurrentSpeed = 0; private float mTotalDistance = 0; private Location mPreviousLocation; private Vector<Location> mTrackedLocations; private LocationListener mLocationListener = null; private Listener mStatusListener = null; private IBinder binder = null; @Override public void onCreate() { super.onCreate(); this.mContext = getApplicationContext(); this.mLocationManager = (LocationManager) this.mContext.getSystemService( Context.LOCATION_SERVICE ); this.mNotificationManager = (NotificationManager) this.mContext.getSystemService( Context.NOTIFICATION_SERVICE ); this.mTrackedLocations = new Vector<Location>(); this.binder = new Binder(); SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this.mContext); binder = new Binder(); if(mTrackingState != Constants.GPS_TRACKING_UNKNOWN) { createListeners(); } } @Override public void onDestroy() { destroyListeneres(); } @Override public IBinder onBind(Intent intent) { return binder; } @Override public boolean onUnbind(Intent intent) { return true; } public boolean acceptLocation(Location proposedLocation) { if(!(proposedLocation.hasSpeed() || proposedLocation.hasAccuracy())) { return false; } else if(proposedLocation.getSpeed() >= MAX_REASONABLE_SPEED) { return false; } return true; } public void updateNotification() { //TODO Alert that no GPS sattelites are available (or are available) } public void startTracking() { this.mTrackingState = Constants.GPS_TRACKING_STARTED; this.mTotalDistance = 0; this.mCurrentSpeed = 0; this.mTrackedLocations = new Vector<Location>(); this.mPreviousLocation = null; createListeners(); } public void pauseTracking() { this.mTrackingState = Constants.GPS_TRACKING_PAUSED; this.mPreviousLocation = null; this.mCurrentSpeed = 0; } public void resumeTracking() { if(this.mTrackingState == Constants.GPS_TRACKING_STOPPED){ this.startTracking(); } this.mTrackingState = Constants.GPS_TRACKING_STARTED; } public void stopTracking() { this.mTrackingState = Constants.GPS_TRACKING_STOPPED; destroyListeneres(); } private void createListeners() { /** * LocationListener receives locations from */ this.mLocationListener = new LocationListener() { @Override public void onStatusChanged(String provider, int status, Bundle extras) { // TODO Auto-generated method stub } @Override public void onProviderEnabled(String provider) { // TODO Auto-generated method stub } @Override public void onProviderDisabled(String provider) { // TODO Auto-generated method stub } @Override public void onLocationChanged(Location location) { if(mTrackingState == Constants.GPS_TRACKING_STARTED && acceptLocation(location)) { if(mPreviousLocation != null) { //Add the distance between the new location and the previous location mTotalDistance += mPreviousLocation.distanceTo(location); } if(location.hasSpeed()) { mCurrentSpeed = location.getSpeed(); } else { mCurrentSpeed = -1; //-1 means speed N/A } mPreviousLocation = location; mTrackedLocations.add(location); } } }; /** * Receives updates reguarding the GPS Status */ this.mStatusListener = new GpsStatus.Listener() { @Override public synchronized void onGpsStatusChanged(int event) { switch( event ) { case GpsStatus.GPS_EVENT_SATELLITE_STATUS: { GpsStatus status = mLocationManager.getGpsStatus( null ); mSatellites = 0; Iterable<GpsSatellite> list = status.getSatellites(); for( GpsSatellite satellite : list ) { if( satellite.usedInFix() ) { mSatellites++; } } updateNotification(); break; } default: break; } } }; } /** * Destroys the LocationListenere and the GPSStatusListener */ private void destroyListeneres() { this.mLocationListener = null; this.mStatusListener = null; } /** * Gets the total distance traveled by the * * @return the total distance traveled (in meters) */ public float getDistance() { return mTotalDistance; } /** * Gets the current speed of the last good location * * @return the current speed (in meters/second) */ public float getSpeed() { return mCurrentSpeed; } } Any assistance would be much appreciated. This is my group's first Android app, and we are a little pressed for time at the moment. The project is for a class, and is available from SourceForge (currently called iTrain, soon to be renamed). Thanks in Advance, Steve

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• select for update problem in jdbc

  - by kartiku

  I'm having a problem with select for update in jdbc. The table i'm trying to update is the smalldb table, i'm having problems-- i'm using select for update which does a lock on the selected row the update statement is -- String updateQ = "UPDATE libra.smalldb SET hIx = ? WHERE name = ?"; the select statement is -- rs = stmt1.executeQuery("SELECT hIx FROM libra.smalldb for update"); rs0 = stmt2.executeQuery("SELECT name,aff FROM libra.smalldb"); the second statement is because i need those fields as well. Here is the complete code -- import java.sql.*; import java.util.ArrayList; import java.util.Collections; public class Jdbcexample1 { /** * @param args */ public static void main(String[] args) { Connection con = null; try { Class.forName("com.mysql.jdbc.Driver").newInstance(); con = DriverManager.getConnection("jdbc:mysql:///test", "root", "*****"); //String url = "jdbc:msql://200.210.220.1:1114/Demo"; //Connection conn = DriverManager.getConnection(url,"",""); Statement stmt1 = con.createStatement(); Statement stmt2 = con.createStatement(); Statement stmt3 = con.createStatement(); Statement stmt4 = con.createStatement(); ResultSet rs0; ResultSet rs; ResultSet rs1; ResultSet rs2; String name; String hIx; int hIxInt; StringBuffer sb = new StringBuffer(); String affiliationSmall; ArrayList<String> affiliation = new ArrayList<String>(); ArrayList<Float> matchValues = new ArrayList<Float>(); ArrayList<Integer> hixValues = new ArrayList<Integer>(); ArrayList<Integer> idValues = new ArrayList<Integer>(); boolean moreFlag = false; String queryString; int tmpIdx; String name1; //get the hix at that index where the similarity is maximum int tmpHidx = 0; int tmpHix = 0; int id = 0; int count; int tmpidIdx = 0; //rs = stmt.executeQuery("SELECT id FROM libra.researchint WHERE id = 910887"); // Get name, affiliation , hIx from smalldb //rs = stmt1.executeQuery("SELECT name,aff,hIx FROM libra.smalldb"); // String cursorName = "OUR_CURSOR"; // stmt1.setCursorName(cursorName); //rs = stmt1.executeQuery("SELECT name,aff,hIx FROM libra.smalldb for update"); rs = stmt1.executeQuery("SELECT hIx FROM libra.smalldb for update"); rs0 = stmt2.executeQuery("SELECT name,aff FROM libra.smalldb"); while ( rs.next() && rs0.next() ) { //String lastName = rs.getString("id"); hIx = rs.getString("hIx"); hIxInt = Integer.parseInt(hIx); //if hIx if (hIxInt==-1) continue; //name = rs.getString("name"); name = rs0.getString("name"); name1 = new String(name); System.out.println(name); //affiliationSmall = rs.getString("aff"); affiliationSmall = rs0.getString("aff"); //name = "\"" +name+ "\""; // Get matching names from large faculty table //String queryString = "SELECT id,name,hIx FROM libra.faculty WHERE name = " +name; //name = does not work names are similar but not same (in faculty and // smalldb) String query = "SELECT id,name,hIx FROM libra.faculty WHERE name like ?"; //String query = "SELECT id,name,hIx FROM libra.faculty for update of hIx WHERE name like ?"; PreparedStatement prepStmt = con.prepareStatement(query); String[] nameArr = name.split(" "); StringBuffer tmpSb = new StringBuffer(); for(int idx = 0;idx<nameArr.length;idx++) { tmpSb.append(nameArr[idx] + "%"); } name = tmpSb.toString(); prepStmt.setString(1, name); rs1 = prepStmt.executeQuery(); //Try to get matching names from faculty big db //Execute the query on faculty table //rs1 = stmt2.executeQuery(queryString); if(rs1.isClosed()) continue; count = 0; matchValues.clear(); affiliation.clear(); while(rs1.next()) { //name = rs1.getString("name"); id = Integer.parseInt(rs1.getString("id")); //idValues.add(id); tmpHix = Integer.parseInt(rs1.getString("hIx")); queryString = "SELECT aff FROM libra.affiliation WHERE id = "+id; rs2 = stmt3.executeQuery(queryString); //affiliation = rs1.getString("aff"); sb.delete(0, sb.length()); while (rs2.next()) { //Concatenate it to the same string using a stringbuffer sb.append(rs2.getString("aff")); //affiliation.add(rs2.getString("aff")); } affiliation.add(sb.toString()); count++; // if(count1) // { // moreFlag = true; // //Call fuzzy match function, store the distance values and select the // //affiliation that has the minimum distance from affiliationSmall // // //problem is here, affiliation.get Index: 2, Size: 2 // // matchValues.add(fuzzyMatch(affiliationSmall,affiliation.get(count))); // hixValues.add(tmpHix); // idValues.add(id); // } }//end of while rs1 -> faculty rs1.close(); int idx = 0; if(count>1) { moreFlag = true; //Call fuzzy match function, store the distance values and select the //affiliation that has the minimum distance from affiliationSmall //problem is here, affiliation.get Index: 2, Size: 2 matchValues.add(fuzzyMatch(affiliationSmall,affiliation.get(idx))); hixValues.add(tmpHix); idValues.add(id); idx++; } if(moreFlag) { Object obj = Collections.max(matchValues); float maxVal = Float.parseFloat(obj.toString()); //int tmpIdx = matchValues.indexOf(new Float(maxVal)); //get the index at which similarity between affiliation strings is maximum, //as returned by fuzzyMatch //int tmpIdx = matchValues.indexOf(maxVal); tmpIdx = matchValues.indexOf(maxVal); //get the hix at that index where the similarity is maximum //int tmpHidx = hixValues.get(tmpIdx); tmpHidx = hixValues.get(tmpIdx); tmpidIdx = idValues.get(tmpIdx); //update the smalldb table String updateQ = "UPDATE libra.smalldb SET hIx = ? WHERE name = ?"; //String updateQ = "UPDATE libra.smalldb SET hIx = ? WHERE current of "+cursorName; //PreparedStatement prepStmt1 = con.prepareStatement("UPDATE libra.smalldb SET hIx = ? WHERE current of "+cursorName); PreparedStatement prepStmt1 = con.prepareStatement(updateQ); //PreparedStatement prepStmt1 = con.prepareStatement(updateQ); prepStmt1.setString(2, name1); prepStmt1.setString(1, Integer.toString(tmpHidx)); prepStmt1.executeUpdate(updateQ); //prepStmt1.execute(); //stmt4.executeUpdate(updateQ); }//end of if //For matching names get the affiliation based on id from affiliation table //con.close(); //System.out.println(lastName); System.out.println(name); }//end of while rs -> smalldb rs.close(); // String updateQ = "UPDATE libra.smalldb1 SET hIx = "+Integer.toString(tmpHidx)+ "WHERE id = "+Integer.toString(tmpidIdx); // stmt4.executeUpdate(updateQ); con.close(); } catch (Exception e) { System.err.println("Got an exception! "); System.err.println(e.getMessage()); e.printStackTrace(); } } public static float fuzzyMatch(String affiliationSmall, String affiliation) { //float distance = 0; String[] temp = null; temp = affiliationSmall.split(" "); int index; //int index1 = affiliation.indexOf(affiliationSmall); int matchCount = 0; for (int idx = 0;idx<temp.length; idx++) { index = affiliation.indexOf(temp[idx]); if (index!=-1) { matchCount++; } } float tmpFloat = matchCount/temp.length; //int[] aff1= new int[affiliation1.length()]; //int[] aff2 = new int[affiliation2.length()]; return tmpFloat; } } i think it is because of the second select statement (rs0) Here is the error- Got an exception! You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?' at line 1 com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?' at line 1 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at com.mysql.jdbc.Util.handleNewInstance(Util.java:409) at com.mysql.jdbc.Util.getInstance(Util.java:384) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1054) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3562) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3494) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1960) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2114) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2690) at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1648) at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1567) at Jdbcexample1.main(Jdbcexample1.java:184)

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• Algorithm for finding symmetries of a tree

  - by Paxinum

  I have n sectors, enumerated 0 to n-1 counterclockwise. The boundaries between these sectors are infinite branches (n of them). The sectors live in the complex plane, and for n even, sector 0 and n/2 are bisected by the real axis, and the sectors are evenly spaced. These branches meet at certain points, called junctions. Each junction is adjacent to a subset of the sectors (at least 3 of them). Specifying the junctions, (in pre-fix order, lets say, starting from junction adjacent to sector 0 and 1), and the distance between the junctions, uniquely describes the tree. Now, given such a representation, how can I see if it is symmetric wrt the real axis? For example, n=6, the tree (0,1,5)(1,2,4,5)(2,3,4) have three junctions on the real line, so it is symmetric wrt the real axis. If the distances between (015) and (1245) is equal to distance from (1245) to (234), this is also symmetric wrt the imaginary axis. The tree (0,1,5)(1,2,5)(2,4,5)(2,3,4) have 4 junctions, and this is never symmetric wrt either imaginary or real axis, but it has 180 degrees rotation symmetry if the distance between the first two and the last two junctions in the representation are equal. Edit: This is actually for my research. I have posted the question at mathoverflow as well, but my days in competition programming tells me that this is more like an IOI task. Code in mathematica would be excellent, but java, python, or any other language readable by a human suffices. Here are some examples (pretend the double edges are single and we have a tree) http://www2.math.su.se/~per/files.php?file=contr_ex_1.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_2.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_5.pdf Example 1 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,3). Example 2 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,1). Example 5 is described as (0,1,4,5)(1,2,3,4) with distances (2). So, given the description/representation, I want to find some algorithm to decide if it is symmetric wrt real, imaginary, and rotation 180 degrees. The last example have 180 degree symmetry. (These symmetries corresponds to special kinds of potential in the Schroedinger equation, which has nice properties in quantum mechanics.)

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• How would you sample a real-time stream of coordinates to create a Speed Graph?

  - by Andrew Johnson

  I have a GPS device, and I am receiving continuous points, which I store in an array. These points are time stamped. I would like to graph distance/time (speed) vs. distance in real-time; however, I can only plot 50 of the points because of hardware constraints. How would you select points from the array to graph? For example, one algorithm might be to select every Nth point from the array, where N results in 50 points total. Code: float indexModifier = 1; if (MIN(50,track.lastPointIndex) == 50) { indexModifier = track.lastPointIndex/50.0f; } index = ceil(index*indexModifier); Another algorithm might be to keep an array of 50 points, and throw out the point with the least speed change each time you get a new point.

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• Animation with Initial Velocity

  - by abustin

  I've been trying to solve this problem for a number of days now but I must be missing something. Known Variables: vi = Initial Velocity t = Animation Duration d = Distance The function I'm trying to create: D(t) = the current distance for a given time Using this information I want to be able to create a smooth animation curve with varying velocity (ease-in/ease-out). The animation must be able ease-in from an initial velocity. The animation must be exactly t seconds and must be travel exactly d units. The curve should lean towards the average velocity with acceleration occurring at the beginning and the end portions of the curve. I'm open to extra configuration variables. The best I've been able to come up with is something that doesn't factor in the initial velocity. I'm hoping someone smarter can help me out. ;) Thank you! p.s. I'm working with an ECMAScript variant

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• Search Lucene with precise edit distances

  - by askullhead

  I would like to search a Lucene index with edit distances. For example, say, there is a document with a field FIRST_NAME; I want all documents with first names that are 1 edit distance away from, say, 'john'. I know that Lucene supports fuzzy searches (FIRST_NAME:john~) and takes a number between 0 and 1 to control the fuzziness. The problem (for me) is this number does not directly translate to an edit distance. And when the values in the documents are short strings (less than 3 characters) the fuzzy search has difficulty finding them. For example if there is a document with FIRST_NAME 'J' and I search for FIRST_NAME:I~0.0 I don't get anything back.

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• How do I save user specific data in an asp.net site?

  - by Greg McNulty

  I just set up user profiles using asp.net 3.5 using wvd. For each user I would like to store data that they will be updating every day. For example, every time they go for a run they will update time and distance. I intend to allow them to also look up their history of distance and time from any past date. My question is, what does the database schema usually look like for such a set up? Currently asp.net set up a db for me when I made user profiles. Do I just add an extra table for every user? Should there be one big table with all users data? How do I relate a user I'd to their specific data? Etc.... I have never done this before so any ideas on how this is usually done would be very helpful. Thank you.

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• How can I shift html-text in the JButton to the left?

  - by Roman

  I use HTML to put text into a JButton. In this way I can play with colors and text size. What I do not like is the distance from the left border of the button and the text (this separation is too large). Is there a way to decrease this distance? I think it should be some parameter in the style of the HTML code. Sample of the code: JButton btn = new JButton("<html><span style='color:#000000; font-size: 11pt;'>" + label + "</span></html>");

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• How do i create a view that can filter unique titles from a checkbox?

  - by buws

  I'm currently creating a view in Drupal that contains a number of fields. What I want to do is to create an exposed filter that is able to filter duplicate titles. The filter would be a checkbox. This is an example of the list NAME TIME RACE DISTANCE John Doe 2.07.54 Boston Marathon 42km Jane Boss 2.15.21 Boston Marathon 42km John Doe 2.02.22 Boston Marathon 42km Jane Boss 2.15.44 Boston Marathon 42km What I want to have is an exposed filter that only shows one unique NAME and sorts it by its best time. The resulting list would look as follows: NAME TIME RACE DISTANCE Jane Boss 2.15.21 Boston Marathon 42km John Doe 2.02.22 Boston Marathon 42km Any help is appreciated!

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• Actionscript 3 3D sizing problem

  - by Simon

  I have an application where I can have an image moving towards the eye. When the image enlarged, I would like to have it resized as 635 px where initial size was 220 px. I have the image with starting position as 0 in z axis. I am wanting to calculate the distance from starting position to the resized image. I have already calculate the distance by hand but when I tried to put it on flash the result is not what i wanted. I am sure that the value I calculated was correct. I know it may be hard to understand my problem. Please help.

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• iPhone Gps logging inaccurate

  - by Martijn

  I'm logging gps points during a walk. Below it shows the function that the coordinates are saved each 5 seconds. i Did several tests but i cannot get the right accuracy i want. (When testing the sky is clear also tests in google maps shows me that the gps signal is good). here is the code: -(void)viewDidAppear:(BOOL)animated{ if (self.locationManager == nil){ self.locationManager = [[[CLLocationManager alloc] init] autorelease]; locationManager.delegate = self; // only notify under 100 m accuracy locationManager.distanceFilter = 100.0f; locationManager.desiredAccuracy= kCLLocationAccuracyBest; [locationManager startUpdatingLocation]; } } - start logging [NSTimer scheduledTimerWithTimeInterval:5 target:self selector:@selector(getData) userInfo:nil repeats:YES]; </code> <code> -(void)getData{ int distance; // re-use location. if ([ [NSString stringWithFormat:@"%1.2f",previousLat] isEqualToString:@"0.00"]){ // if previous location is not available, do nothing distance = 0; }else{ CLLocation *loc1 = [[CLLocation alloc] initWithLatitude:previousLat longitude:previousLong]; CLLocation *loc2 = [[CLLocation alloc] initWithLatitude:latGlobal longitude:longGlobal]; distance = [loc1 getDistanceFrom: loc2]; } // overwrite latGlobal with new variable previousLat = latGlobal; previousLong = longGlobal; // store location and save data to database // this part goes ok } - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation { // track the time to get a new gps result (for gps indicator orb) lastPointTimestamp = [newLocation.timestamp copy]; // test that the horizontal accuracy does not indicate an invalid measurement if (newLocation.horizontalAccuracy < 0) return; // test the age of the location measurement to determine if the measurement is cached // don't rely on cached measurements NSTimeInterval locationAge = -[newLocation.timestamp timeIntervalSinceNow]; if (locationAge > 5.0) return; latGlobal = fabs(newLocation.coordinate.latitude); longGlobal= fabs(newLocation.coordinate.longitude); } I have taken a screenshot of the plot results (the walk takes 30 minutes) and an example of what i'am trying to acomplish: http://www.flickr.com/photos/21258341@N07/4623969014/ i really hope someone can put me in the right direction.

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• MATLAB plot moving data points in seperate subplots simutaneously

  - by Nate B.

  I wish to visualize the movement of a data point throughout space across a period of time within MATLAB. However, the way I want my figure to display is such that only a single instant is plotted at any given time. That was easy, I simply created a for loop to update my 3D plot display for every set of coordinates (x,y,z) in my data. However, I wish to display 4 different viewing angles of this plot at all times. I am well aware of how to setup subplots within MATLAB, that is not the issue. My issue is getting all 4 of these subplots to execute simultaneously so that all 4 subplots are always displaying the same point in time. I would appreciate if anyone could suggest how to handle this issue. As requested, my code for a figure with a single plot is shown below: datan = DATA; %data in form of x,y,z,a,b,c by column for row# of time points tib=zeros(size(datan,1),12); tib(:,1:3) = datan(:,1:3); tib_ref=tib(1,1:3); for i=1:size(datan,1) tib(i,1:3)=tib(i,1:3)-tib_ref; end angle_to_dircos close all figure('Name','Directions (Individual Cycles)','NumberTitle','off') for cc=1:2 hold off for bb=1:10:size(tib,1); scatter3(tib(bb,1),tib(bb,2),tib(bb,3),'green','filled'); %z and y axes are flipped in polhemus system hold on p0 = [tib(bb,1),tib(bb,2),tib(bb,3)]; p1 = [tib(bb,1)+10*tib(bb,4),tib(bb,2)+10*tib(bb,5),tib(bb,3)+10*tib(bb,6)]; p2 = [tib(bb,1)+10*tib(bb,7),tib(bb,2)+10*tib(bb,8),tib(bb,3)+10*tib(bb,9)]; p3 = [-(tib(bb,1)+100*tib(bb,10)),-(tib(bb,2)+100*tib(bb,11)),-(tib(bb,3)+100*tib(bb,12))]; vectarrow(p0,p1,1,0,0) hold on vectarrow(p0,p2,0,1,0) hold on vectarrow(p0,p3,0,0,1) hold on az = 90; el = 0; view(az, el); xlim([-50,50]); ylim([-50,50]); zlim([-50,50]); xlabel('distance from center in X'); ylabel('distance from center in Y'); zlabel('distance from center in Z'); title('XYZ Scatter Plots of Tracker Position'); hold on plot3(0,0,0,'sk','markerfacecolor',[0,0,0]); p0 = [0,0,0]; p1 = [10,0,0]; p2 = [0,10,0]; p3 = [0,0,100]; vectarrow(p0,p1,1,0,0) hold on vectarrow(p0,p2,0,1,0) hold on vectarrow(p0,p3,1,0,1) drawnow; end end

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• plot multi graphs with 2 y axis in 1 graph

  - by lytheone

  Hello, Currently I have a a text file with data at the first row is formatted as follow: time;wave height 1;wave height 2;....... I have column until wave height 19 and rows total 4000 rows. Data in the first column is time in second. From 2nd column onwards, it is wave height elevation which is in meter. I would like to plot the follow: ![alt text][1] on the x axis is time. the left hand side is wave height in m and on the right hand side is the distance between each measurment in a model. inside the graph there are 4 plots, each plot is repersent waveight 1, wave height 2etc at a defined distance related to the right hand side y asix. How would you code this in matlab? I am a begineer, please if you could, it will be very useful to give a bit more explain in your answer! Thank you!!!!!!!!!!

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