Nice Label Algorithm for Charts with minimum ticks

Question

I need to calculate the Ticklabels and the Tickrange for charts manually.

I know the \"standard\" algorithm for nice ticks (see http://books.google.de/books?id=fvA7

Answer 1

Here'a better organized C# code.

public class NiceScale
{

    public double NiceMin { get; set; }
    public double NiceMax { get; set; }
    public double TickSpacing { get; private set; }

    private double _minPoint;
    private double _maxPoint;
    private double _maxTicks = 5;
    private double _range;

    /**
     * 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)
    {
        _minPoint = min;
        _maxPoint = max;
        Calculate();
    }

    /**
     * Calculate and update values for tick spacing and nice
     * minimum and maximum data points on the axis.
     */
    private void Calculate()
    {
        _range = NiceNum(_maxPoint - _minPoint, false);
        TickSpacing = NiceNum(_range / (_maxTicks - 1), true);
        NiceMin = Math.Floor(_minPoint / TickSpacing) * TickSpacing;
        NiceMax = Math.Ceiling(_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, bool 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)
    {
        _minPoint = minPoint;
        _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)
    {
        _maxTicks = maxTicks;
        Calculate();
    }
}