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从昨天开始我就在这个问题上打破了我的头，无法让它工作！我得到的只是一条普通的 x 轴线、y 轴线（甚至没有刻度线或标签！）和图表标题！请帮忙！看似简单，却又如此难以捉摸！

我正在绘制服务器内存使用的最后 5 个值。这些值大约是每分钟（有时是两分钟一次）。例如，我可能想要显示的一组最后 5 个值是这样的：

日期（与）内存使用情况（字节）

2013-05-02 11:50:33 +0000 - 157888512.000000

2013-05-02 11:51:33 +0000 - 157839360.000000

2013-05-02 11:52:14 +0000 - 157888512.000000

2013-05-02 11:56:36 +0000 - 157863936.000000

2013-05-02 11:57:48 +0000 - 157888512.000000

我每分钟刷新一次这个图表。 

'numberForPlot'、'numberOfRecordsForPlot' 似乎被调用了，但图中没有看到/可见的绘图。

我的图表是用这种方法初始化的：

-(void) initializeGraph {

    NSLog(@"View_Visualizer.initializeGraph");

    if ((self.graph == nil) || (self.graph == NULL)) {     

        self.graphHostView = [(CPTGraphHostingView *) [CPTGraphHostingView alloc] initWithFrame:self.view.bounds];

        self.graph = [[CPTXYGraph alloc] initWithFrame:self.graphHostView.bounds];

        graph.paddingLeft   = 10.0;

        graph.paddingRight  = 10.0;

        graph.paddingTop    = 10.0;

        graph.paddingBottom = 10.0;

        graph.title = @"Processor Usage";


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

        NSTimeInterval xLow = 0.0f;

        NSTimeInterval oneMin = 60.0f;

        plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(xLow)

                            length:CPTDecimalFromFloat(oneMin*6.0)];

        plotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0)

                                                    length:CPTDecimalFromFloat(6)];



        // plotting style is set to line plots

        CPTMutableLineStyle *lineStyle = [CPTMutableLineStyle lineStyle];

        lineStyle.lineColor = [CPTColor blackColor];

        lineStyle.lineWidth = 2.0f;



        NSTimeInterval oneMin = 60.0f;

        CPTXYAxisSet *axisSet = (CPTXYAxisSet *) self.graph.axisSet;

        axisSet.xAxis.majorIntervalLength = CPTDecimalFromFloat(oneMin);

        axisSet.xAxis.minorTicksPerInterval = 0;

        axisSet.xAxis.majorTickLineStyle = lineStyle;

        axisSet.xAxis.majorTickLength = 7.0f;

        //axisSet.yAxis.orthogonalCoordinateDecimal = CPTDecimalFromFloat(oneMin);

      //axisSet.xAxis.majorTickLineStyle = lineStyle;

        //axisSet.xAxis.minorTickLineStyle = lineStyle;

        //axisSet.xAxis.axisLineStyle = lineStyle;

        //axisSet.xAxis.minorTickLength = 5.0f;

        //axisSet.xAxis.majorTickLength = 5.0f;

        //axisSet.xAxis.labelOffset = 3.0f;



        NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

        // Example date format : 2013-05-02 11:23:16 +0000

        [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss z"];

        //dateFormatter.dateStyle = kCFDateFormatterShortStyle;

        //dateFormatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];

        CPTTimeFormatter *timeFormatter = [[CPTTimeFormatter alloc] initWithDateFormatter:dateFormatter];

        timeFormatter.referenceDate = [NSDate dateWithTimeIntervalSince1970:([[NSDate date] timeIntervalSince1970] - (6*oneMin))];

        axisSet.xAxis.labelFormatter = timeFormatter;


         //axisSet.yAxis.majorIntervalLength = [NSDecimal decimalNumberWithString:@"5"];

        //axisSet.yAxis.minorTicksPerInterval = 4;

        //axisSet.yAxis.majorTickLineStyle = lineStyle;

        //axisSet.yAxis.minorTickLineStyle = lineStyle;

        //axisSet.yAxis.axisLineStyle = lineStyle;

        //axisSet.yAxis.minorTickLength = 5.0f;

        //axisSet.yAxis.majorTickLength = 5.0f;

        //axisSet.yAxis.labelOffset = 3.0f;



        CPTScatterPlot *xSquaredPlot = [[CPTScatterPlot alloc]

                                    initWithFrame:self.graph.bounds];

        xSquaredPlot.identifier = @"X Squared Plot";

        CPTMutableLineStyle *dataLineStyle = [CPTMutableLineStyle lineStyle];

        dataLineStyle.lineWidth = 1.0f;

        dataLineStyle.lineColor = [CPTColor redColor];

        xSquaredPlot.dataLineStyle = dataLineStyle;

        xSquaredPlot.dataSource = self;


        [self.graph addPlot:xSquaredPlot];


        self.graphHostView.allowPinchScaling = NO;

        self.graphHostView.hostedGraph = self.graph;

        [self.view addSubview:self.graphHostView];

    }
}



#pragma mark - CPTPlotDataSource methods

-(NSUInteger)numberOfRecordsForPlot:(CPTPlot *)plot {

    return [dictHealth count];

}

-(NSNumber *) numberForPlot:(CPTPlot *)plot

                  field:(NSUInteger)fieldEnum

            recordIndex:(NSUInteger)index {

    Health_MemUse *healthData = (Health_MemUse *) [dictHealth objectForKey:                                                          [self.arrayHealthKeys objectAtIndex:index]];


    if ( fieldEnum == CPTScatterPlotFieldX ) {

        return [NSDecimalNumber numberWithFloat:[healthData.currDate timeIntervalSince1970]];

        /*
return [NSNumber numberWithDouble:([healthData.currDate timeIntervalSince1970] + [[NSTimeZone localTimeZone] secondsFromGMT])];
    */

    } else {

        NSLog(@"Plot memuse %f on date %@ for index %d",

          healthData.memUse, healthData.currDate, index);

        return [NSNumber numberWithFloat:(healthData.memUse/(1024*1024*1024))]; // convert bytes to GB

    }
}

请帮忙！我意识到在设置轴的范围时我可能大多是错误的，但我尝试了 Googl'ing、Stackoverflow'ing 并尝试了几种变体，但都是徒劳的。

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