我想什么来完成

我使用核心绘图（1.1）来绘制的条形图，我想以呈现与所述栏下面进一步的细节已经由用户选择（抽头）一个酥料饼。

码

我的代码如下所示：

- (void)barPlot:(CPTBarPlot *)plot barWasSelectedAtRecordIndex:(NSUInteger)idx {

    NSNumber *yValue = self.values[idx];
    NSLog(@"barWasSelectedAtRecordIndex x: %i, y: %@",idx,yValue);

    NSDecimal plotPoint[2];
    NSNumber *plotXvalue = [self numberForPlot:plot
                                         field:CPTScatterPlotFieldX
                                   recordIndex:idx];
    plotPoint[CPTCoordinateX] =
        CPTDecimalFromFloat(plotXvalue.floatValue);

    NSNumber *plotYvalue = [self numberForPlot:plot
                                         field:CPTScatterPlotFieldY
                                   recordIndex:idx];

    plotPoint[CPTCoordinateY] =
        CPTDecimalFromFloat(plotYvalue.floatValue); 

    CPTXYPlotSpace *plotSpace =
        (CPTXYPlotSpace *)graph.defaultPlotSpace;
    CGPoint dataPoint =
        [plotSpace plotAreaViewPointForPlotPoint:plotPoint];
    NSLog(@"datapoint (CGPoint) coordinates tapped: %@",
          NSStringFromCGPoint(dataPoint));

    GrowthChartInfoTableViewController *infoViewController =
        [self.storyboard instantiateViewControllerWithIdentifier:
         @"GrowthChartInfo"];

    self.popover = [[UIPopoverController alloc]
                    initWithContentViewController:infoViewController];
    self.popover.popoverContentSize = CGSizeMake(320, 300);
    self.popover.delegate = self;
    CGRect popoverAnchor =
            CGRectMake(dataPoint.x + graph.paddingLeft,
                       dataPoint.y - graph.paddingTop + graph.paddingBottom,
                       (CGFloat)1.0f, (CGFloat)1.0f);

    [self.popover presentPopoverFromRect:popoverAnchor
                                  inView:self.view
                permittedArrowDirections:UIPopoverArrowDirectionAny
                                animated:YES];
}

我的问题

的酥料饼视图控制器的y位置不正确，它对于每个条不同的，并且对于所述第一杆，其具有负的y值，它呈现在巴而不是下限的上限并隐藏栏。 x位置似乎是正确的。

请帮忙

为什么预期我的代码不能正常工作任何想法？

谢谢！

编辑

根据Eric的答案，我已经更新了我的代码如下：

- (void)barPlot:(CPTBarPlot *)plot barWasSelectedAtRecordIndex:(NSUInteger)idx {

    NSNumber *plotXvalue = [self numberForPlot:plot
                                         field:CPTScatterPlotFieldX
                                   recordIndex:idx];
    NSNumber *plotYvalue = [self numberForPlot:plot
                                         field:CPTScatterPlotFieldY
                                   recordIndex:idx];

    CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)graph.defaultPlotSpace;

    CGPoint cgPlotPoint =
        CGPointMake(plotXvalue.floatValue,
                    plotYvalue.floatValue);
    CGPoint cgPlotAreaPoint =
        [graph convertPoint:cgPlotPoint toLayer:graph.plotAreaFrame.plotArea];

    NSDecimal plotAreaPoint[2];
    plotAreaPoint[CPTCoordinateX] =
        CPTDecimalFromFloat(cgPlotAreaPoint.x);
    plotAreaPoint[CPTCoordinateY] =
        CPTDecimalFromFloat(cgPlotAreaPoint.y);

    CGPoint dataPoint = [plotSpace


           plotAreaViewPointForPlotPoint:plotAreaPoint];
        NSLog(@"datapoint (CGPoint) coordinates tapped: %@",NSStringFromCGPoint(dataPoint));

GrowthChartInfoTableViewController *infoViewController = [self.storyboard 
   instantiateViewControllerWithIdentifier:@"GrowthChartInfo"];



    self.popover = nil;
        self.popover = [[UIPopoverController alloc]


      initWithContentViewController:infoViewController];
    self.popover.popoverContentSize = CGSizeMake(250, 200);
    self.popover.delegate = self;
    CGRect popoverAnchor =
        CGRectMake(dataPoint.x + graph.paddingLeft,
                   dataPoint.y - graph.paddingTop + graph.paddingBottom,
                   (CGFloat)1.0f, (CGFloat)1.0f);

    [self.popover presentPopoverFromRect:popoverAnchor
        inView:self.view
        permittedArrowDirections:UIPopoverArrowDirectionUp
        animated:YES];
}

但是，我得到的结果比以前更错误的。我相信我一定是误解的东西。这里有一些的NSLog的命令的结果：

barWasSelectedAtRecordIndex x: 0, y: -0.03920931548773198848
datapoint (CGPoint) coordinates tapped: {-6388.88, -67024.8}

barWasSelectedAtRecordIndex x: 2, y: 0.174494288286651392
datapoint (CGPoint) coordinates tapped: {-6073.38, -66790}

barWasSelectedAtRecordIndex x: 2, y: 0.174494288286651392
datapoint (CGPoint) coordinates tapped: {-6073.38, -66790}

barWasSelectedAtRecordIndex x: 0, y: -0.03920931548773198848
datapoint (CGPoint) coordinates tapped: {-6388.88, -67024.8}

看来，从酒吧的坐标转换为视图坐标是在我的代码完全错误的。

编辑2

再次感谢您对您的代码示例，埃里克！

我已经更新我的代码，并用下面的选项（y值测试它= 0： plotPoint[CPTCoordinateY] = CPTDecimalFromFloat(0.0f)这导致在一个锚点，其y值似乎是不正确的酥料饼（请参阅以下屏幕截图）。锚点的y值应等同于位置0上的y轴。

然后我试图锚点的y值设定为数据的当前y值。（ plotPoint[CPTCoordinateY] = plotYvalue.decimalValue ）。这导致在一个锚定点的靠近y轴的0值，而不是接近于杆的顶部。然而，y值改变为指示存在可能是与y的值的偏移的问题每个公司（x值）一点点：

我也尝试了额外的转换这埃里克建议dataPoint = [self.view convertPoint:dataPoint fromView:graph.hostingView]但这并没有改变结果。另外，我想补充- graph.paddingTop + graph.paddingBottom到最后的y值，都没有成功。

我将不胜感激什么我的错误可能是任何想法。

谢谢！

该-plotAreaViewPointForPlotPoint:方法返回在绘图区域内的点的坐标系。你需要将其转换成图形的坐标系：

[graph convertPoint:dataPoint fromLayer:graph.plotAreaFrame.plotArea];

该曲线图和其托管视图共享的坐标系。如果self.view不是托管视图，您需要将坐标从主机视图转换为它的坐标系。

更完整的代码示例：

NSDecimal plotPoint[2];
NSNumber *plotXvalue = [self numberForPlot:plot
                                     field:CPTScatterPlotFieldX
                               recordIndex:idx];
plotPoint[CPTCoordinateX] = plotXvalue.decimalValue;

NSNumber *plotYvalue = [self numberForPlot:plot
                                     field:CPTScatterPlotFieldY
                               recordIndex:idx];
plotPoint[CPTCoordinateY] = plotYvalue.decimalValue; 

CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)graph.defaultPlotSpace;

// convert from data coordinates to plot area coordinates
CGPoint dataPoint = [plotSpace plotAreaViewPointForPlotPoint:plotPoint];

// convert from plot area coordinates to graph (and hosting view) coordinates
dataPoint = [graph convertPoint:dataPoint fromLayer:graph.plotAreaFrame.plotArea];

// convert from hosting view coordinates to self.view coordinates (if needed)
dataPoint = [self.view convertPoint:dataPoint fromView:hostingView];

NSLog(@"barWasSelectedAtRecordIndex x: %@, y: %@", plotXvalue, plotYvalue);
NSLog(@"datapoint coordinates tapped: %@", NSStringFromCGPoint(dataPoint));