NiceScale

gistfile1.java

public class NiceScale {

		private double minPoint;
		private double maxPoint;
		private double maxTicks = 10;
		private double tickSpacing;
		private double range;
		private double niceMin;
		private double niceMax;

		/**
		* Instantiates a new instance of the NiceScale class.
		*
		* @param min the minimum data point on the axis
		* @param max the maximum data point on the axis
		*/
		public NiceScale(double min, double max) {
			this.minPoint = min;
			this.maxPoint = max;
			calculate();
		}

		/**
		* Calculate and update values for tick spacing and nice
		* minimum and maximum data points on the axis.
		*/
		private void calculate() {
			this.range = niceNum(maxPoint - minPoint, false);
			this.tickSpacing = niceNum(range / (maxTicks - 1), true);
			this.niceMin =
			Math.floor(minPoint / tickSpacing) * tickSpacing;
			this.niceMax =
			Math.ceil(maxPoint / tickSpacing) * tickSpacing;
		}

		/**
		* Returns a "nice" number approximately equal to range Rounds
		* the number if round = true Takes the ceiling if round = false.
		*
		* @param range the data range
		* @param round whether to round the result
		* @return a "nice" number to be used for the data range
		*/
		private double niceNum(double range, boolean round) {
			double exponent; /** exponent of range */
			double fraction; /** fractional part of range */
			double niceFraction; /** nice, rounded fraction */
	
			exponent = Math.floor(Math.log10(range));
			fraction = range / Math.pow(10, exponent);
	
			if (round) {
				if (fraction < 1.5)
					niceFraction = 1;
				else if (fraction < 3)
					niceFraction = 2;
				else if (fraction < 7)
					niceFraction = 5;
				else
					niceFraction = 10;
			} else {
				if (fraction <= 1)
					niceFraction = 1;
				else if (fraction <= 2)
					niceFraction = 2;
				else if (fraction <= 5)
					niceFraction = 5;
				else
					niceFraction = 10;
			}
	
			return niceFraction * Math.pow(10, exponent);
		}

		/**
		* Sets the minimum and maximum data points for the axis.
		*
		* @param minPoint the minimum data point on the axis
		* @param maxPoint the maximum data point on the axis
		*/
		public void setMinMaxPoints(double minPoint, double maxPoint) {
			this.minPoint = minPoint;
			this.maxPoint = maxPoint;
			calculate();
		}

		/**
		* Sets maximum number of tick marks we're comfortable with
		*
		* @param maxTicks the maximum number of tick marks for the axis
		*/
		public void setMaxTicks(double maxTicks) {
			this.maxTicks = maxTicks;
			calculate();
		}

		/**
		* Gets the tick spacing.
		*
		* @return the tick spacing
		*/
		public double getTickSpacing() {
			return tickSpacing;
		}

		/**
		* Gets the "nice" minimum data point.
		*
		* @return the new minimum data point for the axis scale
		*/
		public double getNiceMin() {
			return niceMin;
		}

		/**
		* Gets the "nice" maximum data point.
		*
		* @return the new maximum data point for the axis scale
		*/
		public double getNiceMax() {
			return niceMax;
		}


}