2D Array removing Duplicates

[dustin kab]

I'm importing a txt file, and then filling the 2D array with the points, all that is working fine. I can't for the life of me get it working where I can find duplicate points and then basically create a new array with only single points, no duplicates.

Since they're coordinates I only want to remove a duplicate POINT, so both X and Y have to match. If only X or only Y match, the points should stay.

I'm using the processing IDE.

float[][] points;


void importCoordinateTextFile(String exportedCoordinates)
{
  String[] strLines = loadStrings(exportedCoordinates);
  points = new float[secondPointsCount][2];
  float xPos=0;
  float yPos=0;
  
  for(int r=0;r<strLines.length;r++)
  {
    //This splits the string and puts it into the strLines array, one coordinate per line
    String[] coordsList = split(strLines[r], ',');
    
   points[r][0] = float(coordsList[0]);
   points[r][1] = float(coordsList[1]);
    
    xPos = float(coordsList[0]);
    yPos = float(coordsList[1]);
    
    findDuplicates(xPos, yPos); 
  }
}

void findDuplicates(float xPos, float yPos)
{
  float count = 0;
   for(int p=0;p<points.length;p++)
   {
     if(points[p][0] == xPos && points[p][1] == yPos)
     {
        count++;
        println("XPos: " + xPos);
        println("Count: " + count);
     } 
   }
}

[Paul Clapham]

Your first step should be to figure out what you want to end up with. An "array"? Okay... what kind of an array? And what should be in it?

[dustin kab]

I want to come up with a 2D array of points that each POINT is an individual. So there are no duplicate points, if there is a cleaner way of simply removing those points and shrinking that Array I would like to do that.

(by POINT I mean, both [x][y] are not the same as any other [x][y])

Ultimate Goal:
- Create a 2D array that contains no duplicate points.

[Campbell Ritchie]

dustin kab wrote:I'm importing a txt file, and then filling the 2D array with the points, all that is working fine. I can't for the life of me get it working where I can find duplicate points and then basically create a new array with only single points, no duplicates.

Since they're coordinates I only want to remove a duplicate POINT, so both X and Y have to match. If only X or only Y match, the points should stay.

I'm using the processing IDE.

float[][] points;


void importCoordinateTextFile(String exportedCoordinates)
{
  String[] strLines = loadStrings(exportedCoordinates);
  points = new float[secondPointsCount][2];
  float xPos=0;
  float yPos=0;
  
  for(int r=0;r<strLines.length;r++)
  {
    //This splits the string and puts it into the strLines array, one coordinate per line
    String[] coordsList = split(strLines[r], ',');
    
   points[r][0] = float(coordsList[0]);
   points[r][1] = float(coordsList[1]);
    
    xPos = float(coordsList[0]);
    yPos = float(coordsList[1]);
    
    findDuplicates(xPos, yPos); 
  }
}

void findDuplicates(float xPos, float yPos)
{
  float count = 0;
   for(int p=0;p<points.length;p++)
   {
     if(points[p][0] == xPos && points[p][1] == yPos)
     {
        count++;
        println("XPos: " + xPos);
        println("Count: " + count);
     } 
   }
}

Welcome to the Ranch

Why don't you put the points into a Set (eg a Tree) as you read them from the text file. Using the return value from the add() method tells you that you have a unique value, and you can add it to your array.

[pedantic mode]There is no such thing as a 2D array in Java™, only an array of arrays.[/pedantic mode]

[dustin kab]

Hey thanks! I've never worked with sets before.

In order to get both points I figured I had to create 2 separate sets.

set.add(coordinates[c][0]);
set2.add(coordinates[c][1]);

I got it going converting 2 single arrays into an array of arrays:

  Float[] xArray = (Float[])set.toArray(new Float[set.size()]);
  Float[] yArray = (Float[])set2.toArray(new Float[set2.size()]);
  
  secondPoints = new float[set.size()][2];
  
  for(int i=0;i<xArray.length;i++)
  {
    secondPoints[i][0] = xArray[i];
    secondPoints[i][1] = yArray[i];
  }

Thanks a ton, if you know how to make this more efficient I'm all ears.

[Paul Clapham]

I think your problem would be a lot less confusing if you just said "I have an array of points and I want to remove all of the duplicates, so I end up with an array of unique points". This business of using a two-dimensional array of floats where each row represents a point (by having exactly two columns) just adds a layer of obfuscation to your problem description.

[dustin kab]

Thanks for the tips, I'll be more clear next time. Either way, it's working now, thanks for the help.