How to cover scattered point???

kir

Hi, I have few set of point in the form (x,y coordinate),I would wish to draw a ellipse (i.e.circle) such that it all points fall within the circle.Would really appreciate if some one can help me .

Thanks in advance !!!!

Chrisir

a nice task!

I appreciate the beauty of the problem.

Chrisir

break it down into smaller steps.

what do you need for a circle?

make a list.

imagine you'd have only 2 points.

Where would you start?

kir

Hi Chrisir thanks for that post !!!

But sorry I didn't get what you said.

Let me explain you where I am exactly struggling .

I am able to draw right angled triangle. Am generating few set of dynamic point (i.e x,y coordinates) these points are scattered all around the region, what I am looking for is that I wish to draw a ellipse or circle in such a way that all points fall with in the region (circle) .

IF you guide me I can send the snapshot of it .

Really looking forward for your reply. Thanks !!!

Chrisir

understood

you need to draw a circle.

what do you need to draw a circle?

kir

hi,

reference point and the radius.

Chrisir

ok, let's say you have only two points

where would the reference point for the circle be?

kir

it can be any one among them . http://www.online-image-editor.com/index.cfm?fa=download_file&image_path=http://imagehost4.online-image-editor.com/oie_upload/images/89214EI12nHArwj/mVivvO6E2bzF.png

Do find the above link for the snap shot of what I am looking for .

Chrisir

No no

I lead you through

again

let's say you have only 2 points P1 and P2

where is the center of the circle then?

HOW can you calulate it?

Chrisir

It's a thought experiment: if you had only 2 points

kir

No I have set of finite points (x,y coordinates) grey circle is one am able to do but it covers extra area but I only need to cover those dense area i.e the pink circle .

colouredmirrorball

Kir, Chrisir is breaking down the problem for you so it's easier to work you towards a solution. Say you only needed to find the circle around two points. Then how would you draw it? Hint,

it can be any one among them

is wrong.

Chrisir

also post your entire code please

kir

@ colouredmirrirorball

Thank u for ur post. POINT IS

http://www.online-image-editor.com/index.cfm?fa=download_file&image_path=http://imagehost4.online-image-editor.com/oie_upload/images/89214EI12nHArwj/mVivvO6E2bzF.png

kir

U find the above url for the snapshot for which i am trying to find the answer.

koogs

"The requested URL /oie_upload/images/89214EI12nHArwj/mVivvO6E2bzF.png was not found on this server."

koogs

(you can upload an image to this forum using the button above the text box, the one on the left that looks like a picture)

kir

I found the grey circle by averaging the set of points (x,y). I took the avg(x,y) as the reference point . I found the distance from this point i.e avg (x,y) to all other points . Among them I took the largest distance as radius and drew a circle from avg (x,y) !!!!!

I want to get only the pink circle as result....

koogs

what grey circle. we cannot see a grey circle because the urls you posted are broken.

kir

@ koogs

I have the image on my desktop !!!!

koogs

i can't see your desktop

kir

@ koogs

To find the below url see if u can access it

http://www.online-image-editor.com/index.cfm?fa=download_file&image_path=http://imagehost4.online-image-editor.com/oie_upload/images/8104983mrVL33/1b0OrOFtZ7Sp.png

koogs

kir

yeah i hope u got my snap shot ???

koogs

were you given an algorithm or do you have to work it out yourself (which is hard)?

luckily someone already has: http://www.personal.kent.edu/~rmuhamma/Compgeometry/MyCG/CG-Applets/Center/centercli.htm

kir

hi Koogs,

I really appreciate ur help.THANKS A TON!!! I am suppose to implement this in processing !!!

Chrisir

I wanted to lead you to understand that you have to take the average of all points positions

Now you write you have that... Why didn't you write that.... also the distance is the right approach

Now it doesn't work... why didn't you say so?

Post your code so we can have a look....

kir

[unformated code deleted, see below]

kir

@ CHRISIR

SORRY !!! Am completely new to this. Sorry do find the above code let me know !!!

GoToLoop

http://forum.Processing.org/two/discussion/8045/how-to-format-code-and-text

kir

thank u GoToLoop for that post !!!!!!!!!!!!!!!!!!

kir

void draw()
{ 
  d1 = dist1[i];
  d2 = dist2[i];
  d3 = dist3[i];

  i++;
  /////////// x and y are calculated based on some condition

  arrx[j] = x;
  arry[j] = y;

  println(arrx[j], arry[j]);

  j++;

  if(j==dist1.length)
  {
    for(int k=j-1; k>1; k--)
    {
      avgx = avgx + arrx[k];
      avgy = avgy + arry[k];
    }
   nx=(avgx/j);
   ny=(avgy/j);

   distx[0] = sqrt(((nx - arrx[1])*(nx - arrx[1])) + ((ny - arry[1])*(ny - arry[1])));
   println(distx[0]);
   for(int k = 1;k<j;k++)
    { 
      distx[k] = sqrt(((nx - arrx[k])*(nx - arrx[k])) + ((ny - arry[k])*(nx - arrx[k])));
        if(distx[k]>=distx[0])
          { 
            distx[0]=distx[k];
            }
    }
    println(distx[0]);

   stroke(0);
   fill(155);
   ellipse(scaleAxis(nx),scaleAxis(ny),scaleAxis(distx[0]),scaleAxis(distx[0]));

   for(int k= 1; k<=j-1;k++)
   {
    ellipse(scaleAxis(arrx[k]),scaleAxis(arry[k]),5,5);
     }

  }

  delay(300);
}

void delay(int wait)
{
  int time = millis();
  while(wait >= (millis() - time));
}

float scaleAxis(float var)
{
  return (150 * var);
}

colouredmirrorball

That code does not look very complete.

koogs

paste code. highlight code. hit ctrl-o.

kir

float X1, Y1, X2, Y2, X3, Y3;
float AB, BC, AC;
float[] dist1, dist2, dist3;
float x, y, prev_x, prev_y;
float d1, d2, d3;
float avgx=0,avgy=0,nx=0,ny=0;
float[] arrx = new float[51];
float[] arry = new float[51];
float[] distx = new float[51];
int i = 0,j = 1;

void setup()
{
  AB = 2;
  BC = 2;
  AC = 2;

  X1 = 0; 
  Y1 = 0;
  X2 = 0;
  Y2 = AB;
  X3 = AC;
  Y3 = 0;
  size(640,560);
  fill(0, 0, 0);
  text("A", scaleAxis(X1), scaleAxis(Y1));
  text("B", scaleAxis(X2), scaleAxis(Y2));
  text("C", scaleAxis(X3), scaleAxis(Y3));

  stroke(0);
  fill(255);

  String[] dist1_str = loadStrings("output_r1.txt");
  String[] dist2_str = loadStrings("output_r2.txt");
  String[] dist3_str = loadStrings("output_r3.txt");

  dist1 = float(dist1_str);
 dist2 = float(dist2_str);
 dist3 = float(dist3_str);

 triangle(scaleAxis(X1), scaleAxis(Y1), scaleAxis(X2), scaleAxis(Y2), scaleAxis(X3), scaleAxis(Y3));
 fill(0);
}

void draw()
{
  d1 = dist1[i];
  d2 = dist2[i];
  d3 = dist3[i];

  i++;

   y = (((d1 *d1) - (d2* d2) + (Y2*Y2) )/ (2*Y2));
   x = (((d1*d1)-(d3*d3)+(X3*X3))/(2*X3)); 
  arrx[j] = x;
  arry[j] = y;

  println(arrx[j], arry[j]);

  j++;

  if(j==dist1.length)
  { 
    for(int k=j-1; k>1; k--)
    {
      avgx = avgx + arrx[k];
      avgy = avgy + arry[k];
    }
   nx=(avgx/j);
   ny=(avgy/j);
    println("averge of x ,y",nx,ny);
   distx[0] = sqrt(((nx - arrx[1])*(nx - arrx[1])) + ((ny - arry[1])*(ny - arry[1])));
   println(distx[0]);
   for(int k = 1;k<j;k++)
    { 
      distx[k] = sqrt(((nx - arrx[k])*(nx - arrx[k])) + ((ny - arry[k])*(nx - arrx[k])));
        if(distx[k]>=distx[0])
          { 
            distx[0]=distx[k];
            }
    }
    println(distx[0]);

   stroke(0);
   fill(155);
   ellipse(scaleAxis(nx),scaleAxis(ny),scaleAxis(distx[0]),scaleAxis(distx[0]));

   for(int k= 1; k<=j-1;k++)
   {
    ellipse(scaleAxis(arrx[k]),scaleAxis(arry[k]),5,5);
     }

  }
delay(300);
}

void delay(int wait)
{
  int time = millis();
  while(wait >= (millis() - time));
}

float scaleAxis(float var)
{
  return (150 * var);
}