Re: Centroid calculations with sparse vectors

[Ted Dunning]

On Thu, May 28, 2009 at 10:56 PM, Shashikant Kore <shashik...@gmail.com>wrote:

> I tried L1 and L2 norms. The centroid definitely looks better, but the
> values are still close to zero.
>

How close is that?  1e-3? (that I would expect) or 1e-300? (that would be
wrong)



> Please let me know if my understanding of L1, L2 norms is correct as
> shown with the code below.
>

You understood what I said, but I said the wrong thing.  See my (oops)
posting a few messages back.


 // L1 Norm  ... centroid is difficult to calculate in a few lines of code

 // what you had for the L1 norm is actually the centroid computation for
the L2 norm
 public Vector computeCentroid() {
 Vector result = new SparseVector(pointTotal.cardinality());
 double sum = pointTotal.zSum();
 for (int i = 0; i < pointTotal.cardinality(); i++)
   result.set(i, pointTotal.get(i) / sum);  // Dividing each coordinate
value by the
sum of all weights
 return result;
 }