尽管设置了 xRange，但数据绘制在错误的位置

Question

我正在尝试绘制直方图。 x 轴范围应约为 881 到 1281（我已验证在为 xRange 构建 CPTPlotRange 时我使用的位置为 881，范围为 400）。轴绘制的范围正确，但我的条形图最终接近 2000（数据 space），即使我的数据源方法发送的位置值介于 881 和 1281 之间。

代码如下：

- (void)
viewDidLoad
{
    [super viewDidLoad];

    InputVariable           temp(1081.0, 50.0);
    self.hist = new Histogram(temp.mean(), temp.stdDev(), 5.0);
    for (Histogram::SizeT i = 0; i < 1000; ++i)
    {
        double v = temp.randomValue();
        self.hist->add(v);
    }

    const Histogram& hist = *self.hist;

    CPTXYGraph* graph = [[CPTXYGraph alloc] initWithFrame: self.chart1.bounds];
    graph.fill                = [CPTFill fillWithColor: [CPTColor lightGrayColor]];
    graph.cornerRadius        = 4.0;
    self.chart1.hostedGraph = graph;

    self.graph = graph;

    // Plot area

    graph.plotAreaFrame.fill          = [CPTFill fillWithColor:[CPTColor lightGrayColor]];
    graph.plotAreaFrame.paddingTop    = 4.0;
    graph.plotAreaFrame.paddingBottom = 50.0;
    graph.plotAreaFrame.paddingLeft   = 50.0;
    graph.plotAreaFrame.paddingRight  = 4.0;
    graph.plotAreaFrame.cornerRadius  = 4.0;
    graph.plotAreaFrame.masksToBorder = NO;

    graph.plotAreaFrame.axisSet.borderLineStyle = [CPTLineStyle lineStyle];

    graph.plotAreaFrame.plotArea.fill = [CPTFill fillWithColor:[CPTColor whiteColor]];

    // Setup plot space
    CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)graph.defaultPlotSpace;
    plotSpace.xRange     = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromDouble(hist.lowValue()) length:CPTDecimalFromDouble(hist.range())];
    plotSpace.yRange     = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromDouble(0.0) length:CPTDecimalFromDouble(hist.maxBinCount() * 1.2)];
    //plotSpace.yScaleType = CPTScaleTypeLog;

    // Line styles
    CPTMutableLineStyle *axisLineStyle = [CPTMutableLineStyle lineStyle];
    axisLineStyle.lineWidth = 2.0;
    //axisLineStyle.lineCap   = kCGLineCapRound;

    CPTMutableLineStyle *majorGridLineStyle = [CPTMutableLineStyle lineStyle];
    majorGridLineStyle.lineWidth = 0.75;
    majorGridLineStyle.lineColor = [CPTColor redColor];

    CPTMutableLineStyle *minorGridLineStyle = [CPTMutableLineStyle lineStyle];
    minorGridLineStyle.lineWidth = 0.25;
    minorGridLineStyle.lineColor = [CPTColor blueColor];

    // Text styles
    CPTMutableTextStyle *axisTitleTextStyle = [CPTMutableTextStyle textStyle];
    axisTitleTextStyle.fontName = @"Helvetica Neue Bold";
    axisTitleTextStyle.fontSize = 14.0;

    // Axes
    // Label x axis with a fixed interval policy
    CPTXYAxisSet *axisSet = (CPTXYAxisSet *)graph.axisSet;
    CPTXYAxis *x          = axisSet.xAxis;
    x.separateLayers              = NO;
    x.orthogonalCoordinateDecimal = CPTDecimalFromDouble(0.0);
    x.majorIntervalLength         = CPTDecimalFromDouble(0.5);
    x.minorTicksPerInterval       = 4;
    x.tickDirection               = CPTSignNone;
    x.axisLineStyle               = axisLineStyle;
    x.majorTickLength             = 12.0;
    x.majorTickLineStyle          = axisLineStyle;
    //x.majorGridLineStyle          = majorGridLineStyle;
    x.minorTickLength             = 8.0;
    //x.minorGridLineStyle          = minorGridLineStyle;
    x.title                       = @"Temperature";
    x.titleTextStyle              = axisTitleTextStyle;
    x.titleOffset                 = 25.0;
    //x.alternatingBandFills        = @[[[CPTColor redColor] colorWithAlphaComponent:0.1], [[CPTColor greenColor] colorWithAlphaComponent:0.1]];
    x.labelingPolicy              = CPTAxisLabelingPolicyAutomatic;

    // Label y with an automatic label policy.
    //axisLineStyle.lineColor = [CPTColor greenColor];

    CPTXYAxis *y = axisSet.yAxis;
    y.separateLayers        = YES;
    y.orthogonalCoordinateDecimal = plotSpace.xRange.location;//CPTDecimalFromDouble(hist.lowValue());
    y.minorTicksPerInterval = 9;
    y.tickDirection         = CPTSignNone;
    y.axisLineStyle         = axisLineStyle;
    y.majorTickLength       = 12.0;
    y.majorTickLineStyle    = axisLineStyle;
    //y.majorGridLineStyle    = majorGridLineStyle;
    //y.minorTickLength       = 8.0;
    //y.minorGridLineStyle    = minorGridLineStyle;
    y.title                 = @"Number of Samples";
    y.titleTextStyle        = axisTitleTextStyle;
    y.titleOffset           = 40.0;
    //y.alternatingBandFills  = @[[[CPTColor blueColor] colorWithAlphaComponent:0.1], [NSNull null]];
    y.labelingPolicy        = CPTAxisLabelingPolicyAutomatic;

    //CPTFill *bandFill = [CPTFill fillWithColor:[[CPTColor darkGrayColor] colorWithAlphaComponent:0.5]];
    //[y addBackgroundLimitBand:[CPTLimitBand limitBandWithRange:[CPTPlotRange plotRangeWithLocation:CPTDecimalFromDouble(7.0) length:CPTDecimalFromDouble(1.5)] fill:bandFill]];
    //[y addBackgroundLimitBand:[CPTLimitBand limitBandWithRange:[CPTPlotRange plotRangeWithLocation:CPTDecimalFromDouble(1.5) length:CPTDecimalFromDouble(3.0)] fill:bandFill]];


    //  Set up the bar plot…

    //CPTXYPlotSpace *barPlotSpace = [[CPTXYPlotSpace alloc] init];
    CPTXYPlotSpace *barPlotSpace = (CPTXYPlotSpace *) self.graph.defaultPlotSpace;

    //barPlotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromDouble(0.0) length:CPTDecimalFromDouble(200.0)];
    //barPlotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromDouble(0.0) length:CPTDecimalFromDouble(15.00)];
    //[self.graph addPlotSpace:barPlotSpace];

    CPTBarPlot *barPlot = [CPTBarPlot tubularBarPlotWithColor:[CPTColor darkGrayColor] horizontalBars: false];
    barPlot.dataSource      =   self;

    barPlot.barsAreHorizontal = false;
    barPlot.barWidth        =   CPTDecimalFromDouble(1.0);
    barPlot.barBasesVary    =   false;
    barPlot.baseValue       =   CPTDecimalFromDouble(0.0);
    barPlot.barOffset       =   CPTDecimalFromDouble(hist.lowValue());
    barPlot.identifier      =   @"Bar Plot";
    //barPlot.plotRange     =   [CPTPlotRange plotRangeWithLocation:CPTDecimalFromDouble(0.0) length:CPTDecimalFromDouble(7.0)];

    CPTMutableTextStyle *whiteTextStyle = [CPTMutableTextStyle textStyle];
    whiteTextStyle.color = [CPTColor whiteColor];
    //barPlot.labelTextStyle    = whiteTextStyle;

    [self.graph addPlot:barPlot toPlotSpace:barPlotSpace];
}


- (NSUInteger)
numberOfRecordsForPlot: (CPTPlot*) inPlot
{
    return self.hist->numBins();
}

- (double)
doubleForPlot: (CPTPlot*) inPlot
    field: (NSUInteger) inField
    recordIndex: (NSUInteger) inIdx
{
    const Histogram& h = *self.hist;

    if (inField == CPTBarPlotFieldBarLocation)
    {
        double v = h.binMid(inIdx);
        NSLog(@"v: %f", v);
        return v;
    }
    else if (inField == CPTBarPlotFieldBarTip)
    {
        return h[inIdx];
    }

    return 0.0;
}

结果图：

知道我做错了什么吗？谢谢！

Answer 1

对于此应用程序，barOffset 应为零 (0)。偏移量用于从数据源给定的位置移动条形图。最常见的用途是在同一图表上绘制多个条形图时在同一位置分隔条形图，这些条形图可能在公共位置有重叠条形图。

尽管设置了 xRange，但数据绘制在错误的位置

Despite setting xRange, data is plotted in the wrong place

core-plot