code: public void setValueAt( int index, double value ) {
  
          int row = index / data[0].length;
          int col = index % data[0].length;
  
          data[row][col] = value;
      }
docs: /*
  (non-Javadoc)
  
  @see eu.hydrologis.jgrass.libs.map.RasterData#setValueAt(int)