JFreeChart LogAxis Frequency/Resistance multipliers

Question

I'm trying to figure out how to dynamically format the values on the axes of my line chart based on the multiplier.

I'm using LogAxis for both the X and Y axes, as follows:

  final LogAxis rangeAxis = new LogAxis(valueAxisLabel);
  rangeAxis.setStandardTickUnits(LogAxis.createLogTickUnits(Locale.ENGLISH));
  rangeAxis.setRange(0.01, 10.0);  //10 mOhms to 10 Ohms
  plot.setRangeAxis(rangeAxis);

  final LogAxis domainAxis = new LogAxis(frequencyAxisLabel);
  domainAxis.setStandardTickUnits(LogAxis.createLogTickUnits(Locale.ENGLISH));
  domainAxis.setRange(100, 10000000); //100Hz to 10MHz
  plot.setDomainAxis(domainAxis);

I currently have the following values on my Y axis:
0.01, 0.1, 1, 10
But would like it to display as
10mOhm, 100mOhm, 1Ohm, 10Ohm

and on the X axis I have
100, 1,000, 10,000, 100,000, 1,000,000, 10,000,000
but would like to see
100Hz, 1kHz, 10kHz, 100kHz, 1MHz, 10MHz

I know you can override the NumberFormat used on the axis, but I haven't found a way to do so to where the NumberFormat is overridden dynamically based on the value like this. Is this possible? Do I need to extend NumberFormat to do this?

EDIT: Per the accepted answer, I extended NumberFormat as follows (Note that the implementation isn't complete but rather hacked for quick demo purposes for my boss)

public class UnitNumberFormat extends NumberFormat
{
   /**
    * 
    */
   private static final long serialVersionUID = -8544764432101798895L;

   private UnitValue unitValue;


   public UnitNumberFormat(UnitValue unitValue)
   {
      super();
      this.unitValue = unitValue;
   }


   /*
    * (non-Javadoc)
    * @see java.text.NumberFormat#format(double, java.lang.StringBuffer,
    * java.text.FieldPosition)
    */
   @Override
   public StringBuffer format(double number, StringBuffer toAppendTo, FieldPosition pos)
   {
      StringBuffer formattedValue = new StringBuffer();
      BigDecimal bd = new BigDecimal(number);
      BigDecimal multiplier = new BigDecimal(1);
      String multiplierString = "";
      if(number < 1 && number > 0)
      {
         multiplier = new BigDecimal(1000);
         multiplierString = "m";
      }
      else if(number < 1000 && number >= 1)
      {
         multiplier = new BigDecimal(1);
         multiplierString = "";
      }
      else if(number < 1000000 && number >= 1000)
      {
         multiplier = new BigDecimal(1. / 1000);
         multiplierString = "k";
      }
      else if(number < 1000000000 && number >= 1000000)
      {
         multiplier = new BigDecimal(1. / 1000000);
         multiplierString = "M";
      }
      else
      {
         throw new NumberFormatException("This formatter doesn't yet support values beyond Mega");
      }

      bd = bd.multiply(multiplier).round(new MathContext(1, RoundingMode.HALF_UP));

      formattedValue.append(bd.toPlainString());
      formattedValue.append(" ");
      formattedValue.append(multiplierString);
      formattedValue.append(this.unitValue.getUnit());

      return formattedValue;
   }


   /*
    * (non-Javadoc)
    * @see java.text.NumberFormat#format(long, java.lang.StringBuffer,
    * java.text.FieldPosition)
    */
   @Override
   public StringBuffer format(long number, StringBuffer toAppendTo, FieldPosition pos)
   {
      return null;
   }


   /*
    * (non-Javadoc)
    * @see java.text.NumberFormat#parse(java.lang.String,
    * java.text.ParsePosition)
    */
   @Override
   public Number parse(String source, ParsePosition parsePosition)
   {
      return null;
   }

}

and UnitValue is as follows:

public enum UnitValue {
   HERTZ("Hz"),

   OHMS("Ω"),

   ;

   private final String unit;


   private UnitValue(String unit)
   {
      this.unit = unit;
   }


   /**
    * @return the unit
    */
   public String getUnit()
   {
      return unit;
   }
}

Answer 1

Yes you do need to subclass NumberFormat there is an example here