Method getOnlineColumnStats

JSAT/src/jsat/DataSet.java:275–309

Returns summary statistics computed in an online fashion for each numeric variable. This returns all summary statistics, but can be less numerically stable and uses more memory. NaNs / missing values will be ignored in the statistics for each column. @param useWeights true to return th

(boolean useWeights)

     * @return an array of summary statistics
     */
    public OnLineStatistics[] getOnlineColumnStats(boolean useWeights)
    {
        OnLineStatistics[] stats = new OnLineStatistics[numNumerVals];
        for(int i = 0; i < stats.length; i++)
            stats[i] = new OnLineStatistics();
        
        double totalSoW = 0.0;
        
        /**
         * We got to skip nans, count their weight in each column so that we can still fast count zeros
         */
        double[] nanWeight = new double[numNumerVals];
        
        for(Iterator<DataPoint> iter = getDataPointIterator(); iter.hasNext(); )
        {
            DataPoint dp = iter.next();
            
            double weight = useWeights ? dp.getWeight() : 1;
            totalSoW += weight;

            Vec v = dp.getNumericalValues();
            for (IndexValue iv : v)
                if (Double.isNaN(iv.getValue()))//count it so we can fast count zeros right later
                    nanWeight[iv.getIndex()] += weight;
                else
                    stats[iv.getIndex()].add(iv.getValue(), weight);
        }
        
        double expected = totalSoW;
        //Add zero counts back in
        for(int i = 0; i < stats.length; i++)
            stats[i].add(0.0, expected-stats[i].getSumOfWeights()-nanWeight[i]);
        
        return stats;
    }
    
    /**
     * Returns an {@link OnLineStatistics } object that is built by observing