code: public void setValueR(int x, int y, double value) {
  		int idx=y*width+x;
  		setValueR_atIndex(idx, value);
  	}
docs: Sets the real part at the specified position
  <br>
  If {@link #isSynchronizePowerSpectrum()} is true, then this will also
  update the corresponding power value.
  @param x coordinate
  @param y coordinate
  @param value to be set