Creating a set of points

Programming Questions

dusker1

in Programming Questions • 2 years ago

I've been using Lee Byron's mesh library and basically I want to create a set of points.

for(int c=0;c<coordinates.length;c++)
{
OUTPUT.println(coordinates[c][0] + "," + coordinates[c][1] + "," + p + "," + "Coordinate");
set.add(point(coordinates[c][0],coordinates[c][1]));
}

I get this error:

The method add(Object) in the type Set is not applicable for the arguments (void)

I was curious as to how I could either turn these coordinates into an object, or work around whats happening here and just plug the points into the set.

Replies(12)

cedrickie..

not really sure what "set" is is your case but thats not how you use the mesh library. you are creating an array of points and pass that array when creating the voronoi or delaunay object.
why not follow his examples : http://www.leebyron.com/else/mesh/

dusker1

Re: Creating a set of points

2 years ago

Oh sorry, I have lengthy code creating Voronoi's that works fine.

Basically what I need is a way to create a Set of Points. I have all the points I want to add, the trouble is there are some duplicate points and Voronoi's hate duplicate points thus a Set would remove those duplicates.

I just need further instruction on creating a Set of Points.

Currently I am attempting it with:

Set set = new HashSet();

PhiLho

Re: Creating a set of points

2 years ago

Ah, OK. So you get this error because you try to add the result of point() which is just a function drawing a point on screen, not returning anything.
You might want to make your coordinates array a mono-dimension array of PVector instead. Thus, you can add each instance of PVector to your Set. Since PVector implements equals() and hashCode(), it should work smoothly.

dusker1

Re: Creating a set of points

2 years ago

PVector xy;
Set set = new HashSet();
for(int c=0;c<coordinates.length;c++)
{
xy = new PVector(coordinates[c][0],coordinates[c][1]);
set.add(xy);
}

All of the elements add, set doesn't seem to be able to tell the difference.

The println statement is correct for what I want at least, it's [x, y, z].

I was wondering if there would be a different approach to adding these elements to a set?

PhiLho

Re: Creating a set of points

2 years ago

" All of the elements add, set doesn't seem to be able to tell the difference."
Not sure if you report success or failure...

dusker1

Re: Creating a set of points

2 years ago

My bad, it adds Every coordinate to the set, it doesn't leave out duplicates. They're all there in the set, duplicate or not. So it's a failure.

PhiLho

Re: Creating a set of points

2 years ago

I deleted a duplicate thread: there is no reason to create a new thread asking the same questions than here.
At least, it answered my question above.
I don't know what doesn't work for you. If I make a simple test, it works for me:

Set set = new HashSet();
PVector[] coordinates =
{
new PVector(3.14, 6.11),
new PVector(2.24, 4.21),
new PVector(1.13, 1.11),
new PVector(4.01, 5.17),
new PVector(3.14, 6.11),
new PVector(2.24, 4.21),
new PVector(5.54, 6.15),
};
for (PVector coord : coordinates)
{
set.add(coord);
}
println(set);

Note: PVector's equals() compares floats with == which is generally said to be bad practice, as 6.1154545 and 6.1154546 can be seen as equals for some purposes: some float comparison functions use the concept of epsilon, a small value: if the absolute value of the difference between the the two values is below epsilon, they are seen as equal.

dusker1

Re: Creating a set of points

2 years ago

Hmm, I don't need a set of all the PVectors, I need to eliminate duplicates.

Because i noticed even in your example it kept all of the coordinates, it didn't eliminate duplicates. Even if you switch all the points to whole numbers, they will all still appear in the set.

PhiLho

Re: Creating a set of points

2 years ago

Either we don't have the same JVM (unlikely...) or we don't have the same definition of duplicates...
In my example, there are 7 PVectors added to the Set, and it holds (and display) only 5, so 2 are "eliminated".

dusker1

Re: Creating a set of points

2 years ago

Sadly this is the output I get from the example. Is there further logic that you apply to take out the duplicates? I would like Sets to work for me, it seems like that should be all that I have to do.

Let me know if I'm just missing something that cleans these up!

PhiLho

Re: Creating a set of points

2 years ago

Ah, I see. You use 1.2.1 while I used 0193. Looks like equals() and hashCode() have been implemented only recently.
OK, it can be solved easily:

void setup()
{
Set set = new HashSet();
PVector[] coordinates =
{
new PVector2(3.14, 6.11),
new PVector2(2.24, 4.21),
new PVector2(1.13, 1.11),
new PVector2(4.01, 5.17),
new PVector2(3.14, 6.11),
new PVector2(2.24, 4.21),
new PVector2(5.54, 6.15),
};
for (PVector coord : coordinates)
{
set.add(coord);
}
println(set);
exit();
}
class PVector2 extends PVector
{
PVector2(float x, float y) { super(x, y); }
public boolean equals(Object obj) {
if (!(obj instanceof PVector))
return false;
final PVector p = (PVector) obj;
return x == p.x && y == p.y && z == p.z;
}
public int hashCode() {
int result = 1;
result = 31 * result + Float.floatToIntBits(x);
result = 31 * result + Float.floatToIntBits(y);
result = 31 * result + Float.floatToIntBits(z);
return result;
}
}

I just pasted the functions I found in the latest version of PVector.java.

dusker1

Re: Creating a set of points

2 years ago

Thanks for your help, I just switched to using 0194 and it works perfectly. Didn't know the version I was using was so old.

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