code: @Pure
  	public DoubleProperty firstAxisExtentProperty() {
  		if (this.extentR == null) {
  			this.extentR = new SimpleDoubleProperty(this, MathFXAttributeNames.FIRST_AXIS_EXTENT) {
  				@Override
  				protected void invalidated() {
  					if (get() < 0.) {
  						set(0.);
  					}
  				}
  			};
  		}
  		return this.extentR;
  	}
docs: Replies the property for the extent of the first axis.
  
  @return the firstAxisExtent property.