DateAxis formatting

Thanks Andrew. I tried usingthe SubDayTextFormatting parameter (both with and without a TextFormatting parameter) but it made no apparent difference.

Regards,
Mike

Hi Mike,

My mistake. I looked in the code and because CategoryDateTimeAxis is a special case, we format labels according to the level of zoom.

All of this label formatting is handled by the TradeChartAxisLabelProvider class, which is attached by default to the CategoryDateTimeAxis.LabelProvider property.

The source for the TradeChartAxisLabelProvider is included below. I’m hoping you can take this and modify it to meet your needs.

/// <summary>
/// A LabelFormatter instance to use on stock charts. Designed to be used with the <see cref="CategoryDateTimeAxis"/> and applied by default on the <see cref="SciStockChart"/> control
/// </summary>
public class TradeChartAxisLabelProvider : LabelProviderBase
{
    private readonly string[] _cursorFormatStrings = new[]
        {
            "MMM {0}",
            "yyyy {0}",
            "{0} yyyy",
            "dd MMM {0}", 
        };

    private readonly string[] _majorFormatStrings = new[]
        {
            "yyyy",
            "MMM",
            "dd MMM",
            "HH:mm"
        };

    private int _formatIndex;

    /// <summary>
    /// Called when the label formatted is initialized, with the parent axis instance
    /// </summary>
    /// <param name="parentAxis">The parent <see cref="IAxis" /> instance</param>
    /// <exception cref="System.InvalidOperationException">The TradeChartAxisLabelFormatter is only valid on instances of CategoryDateTimeAxis</exception>
    public override void Init(IAxisCore parentAxis)
    {
        var catAxis = parentAxis as CategoryDateTimeAxis;
        if (catAxis == null)
        {
            throw new InvalidOperationException("The TradeChartAxisLabelFormatter is only valid on instances of CategoryDateTimeAxis");
        }

        base.Init(parentAxis);
    }

    /// <summary>
    /// Called at the start of an axis render pass, before any labels are formatted for the current draw operation
    /// </summary>
    public override void OnBeginAxisDraw()
    {
        var catAxis = (CategoryDateTimeAxis)ParentAxis;

        var barTimeFrame = catAxis.GetBarTimeFrame();
        var visibleRangeAsDateRange = catAxis.ToDateRange((IndexRange)catAxis.VisibleRange);

        _formatIndex = 3;

        if (visibleRangeAsDateRange != null && visibleRangeAsDateRange.IsDefined)
        {
            long ticksInViewport = visibleRangeAsDateRange.Diff.Ticks;

            if (ticksInViewport > TimeSpanExtensions.FromYears(2).Ticks)
            {
                _formatIndex = 0;
            }
            else if (ticksInViewport > TimeSpan.FromDays(14).Ticks || barTimeFrame >= TimeSpan.FromDays(1).Ticks)
            {
                _formatIndex = -1;
            }
        }

        base.OnBeginAxisDraw();
    }

    /// <summary>
    /// Formats a label for the cursor, from the specified data-value passed in
    /// </summary>
    /// <param name="dataValue">The data-value to format</param>
    /// <returns>
    /// The formatted cursor label string
    /// </returns>
    public override string FormatCursorLabel(IComparable dataValue)
    {
        string formattedText;

        var dateTime = dataValue.ToDateTime();
        if (ParentAxis.CursorTextFormatting.IsNullOrEmpty())
        {
            int index = GetFormattingIndex(dateTime, true);

            formattedText = string.Format(dateTime.ToString(_cursorFormatStrings[index]),
                                 dateTime.ToString(_majorFormatStrings[index]));
        }
        else
        {
            formattedText = dateTime.ToString(ParentAxis.CursorTextFormatting);
        }

        return formattedText;
    }

    /// <summary>
    /// Formats a label for the axis from the specified data-value passed in
    /// </summary>
    /// <param name="dataValue">The data-value to format</param>
    /// <returns>
    /// The formatted label string
    /// </returns>
    public override string FormatLabel(IComparable dataValue)
    {
        var dateTime = dataValue.ToDateTime();

        var index = GetFormattingIndex(dateTime);

        var formatString = _majorFormatStrings[index];
        var formattedValue = dateTime.ToString(formatString);

        return formattedValue;
    }

    private int GetFormattingIndex(DateTime dataValue, bool forCursor = false)
    {
        var index = _formatIndex;

        if (index < 0)
        {
            index = 2;

            if (dataValue.Day == 1 && !forCursor)
            {
                index = 1;
            }
        }

        return index;
    }
}

Alternatively, if you’re not interested in the gap-collapsing ability of CategoryDateTimeAxis, there is the DateTimeAxis which is far simpler and respects TextFormatting and SubDayTextFormatting.

Best regards,
Andrew

Thanks Andrew. As I mentioned in my original post I started out by usingthe DateTimeAxis but I got some very odd behaviour with the automatic range setting – the X axis covered a peridod of 24-48 hours with all my data in a vertical line somewhere near the centre!

I’ll have anotheer try with it to see if I can get something sensible.

Reagrds,
MIke

Hi Mike,

CategoryDateTimeAxis and DateTimeAxis have two text formatting properties:

• TextFormatting

• SubDayTextFormatting (used when VisibleRange shows less than a day)

You can find out more, as well as how to dynamically change text formatting at the following links:

1. Axis Labels – TextFormatting and CursorTextFormatting]
2. LabelProvider API – Full Control over Axis Labels

Best regards,

Andrew