docs: public void addSample( double[] sampleData ) {
          if( A.getNumCols() != sampleData.length )
              throw new IllegalArgumentException("Unexpected sample size");
          if( sampleIndex >= A.getNumRows() )
              throw new IllegalArgumentException("Too many samples");
  
          for( int i = 0; i < sampleData.length; i++ ) {
              A.set(sampleIndex,i,sampleData[i]);
          }
          sampleIndex++;
      }