在x轴上的月份的核心图（iphone）

Question

我想在iphone上使用coreplot绘制一个XY图，其中x轴上的日期和y轴上的一些值。参考使用coreplot SDK发布的DatePlot示例，我能够以月为单位在x轴上绘制日期图形（即x从月份的1日期到最后日期）。现在我想要一个年度量表，即我想在x轴上显示所有月份名称（1月，2月，3月等），并将我的剔号间隔显示为一个月的时间。

我用下面的代码显示值月度规模现在

oneXUnit  = 60 * 60 * 24; 
x.majorIntervalLength = CPDecimalFromFloat((float) oneXUnit); 
NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init]autorelease]; 
NSString *dateString  = @"0"; 
[dateFormatter setDateFormat:@"MM"]; 
CPTimeFormatter *timeFormatter = [[CPTimeFormatter alloc]initWithDateFormatter:dateFormatter]; 
timeFormatter.referenceDate = [dateFormatter dateFromString:dateString]; 
x.labelFormatter = timeFormatter; 

对于每年的模式X剔inteval需要为一个月。我试了下面的代码，但没有工作

oneXUnit  = 60 * 60 * 24 * 30; 
x.majorIntervalLength = CPDecimalFromFloat((float) oneXUnit); 
NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init]autorelease]; 
NSString *dateString  = @"Jan"; 
[dateFormatter setDateFormat:@"MMM"]; 
CPTimeFormatter *timeFormatter = [[CPTimeFormatter alloc]initWithDateFormatter:dateFormatter]; 
timeFormatter.referenceDate = [dateFormatter dateFromString:dateString]; 
x.labelFormatter = timeFormatter; 

我认为这种逻辑失败，因为每个月的天数是不同的。现在有几个月在x轴上显示，但它显示为

一月，三月，四月，五月，五月，六月，七月，八月，九月，十月，十一月，十二月。

您可以看到没有Feb，并且有5个条目。我的滴答时间间隔如何与每个月的天数相关联。任何解决方案 感谢和问候，

Answer 1

我有同样的问题。我的快速&肮脏的解决方案是做自定义标签，循环所有月份并添加时间戳到一个数组。

x.labelingPolicy = CPAxisLabelingPolicyNone; 

NSMutableArray *customLabels = [NSMutableArray arrayWithCapacity:12]; 
NSMutableArray *customMajorTickLocations = [NSMutableArray arrayWithCapacity:12]; 
NSMutableArray *customMinorTickLocations = [NSMutableArray arrayWithCapacity:12]; 
NSDate* dateCurrentMonth = [[NSDate date] dateAtStartOfYear]; 

for (NSUInteger iMonth = 0; iMonth < 12; iMonth++) 
{ 
    NSNumber* numMajorTickLocation = [NSNumber numberWithDouble:[dateCurrentMonth timestampAtMidnight]]; 
    NSNumber* numMinorTickLocation = [NSNumber numberWithDouble:[dateCurrentMonth timestampAtMidnight]+14*oneDay]; 

CPAxisLabel *newLabel = [[CPAxisLabel alloc] initWithText:[dateFormatter stringFromDate:dateCurrentMonth] textStyle:x.labelTextStyle]; 
newLabel.tickLocation = [numMinorTickLocation decimalValue]; 
newLabel.offset = x.labelOffset + x.majorTickLength; 

dateCurrentMonth = [[dateCurrentMonth dateByAddingDays:32] dateAtStartOfMonth]; 

[customLabels addObject:newLabel]; 
[customMajorTickLocations addObject:numMajorTickLocation]; 
[customMinorTickLocations addObject:numMinorTickLocation]; 
[newLabel release]; 

} 

// add a last major tick to close the range 
[customMajorTickLocations addObject:[NSNumber numberWithDouble:[dateCurrentMonth timestampAtMidnight]]]; 

x.axisLabels = [NSSet setWithArray:customLabels]; 
x.majorTickLocations = [NSSet setWithArray:customMajorTickLocations]; 
x.minorTickLocations = [NSSet setWithArray:customMinorTickLocations]; 

Answer 2

刚刚在相关问题中回答。使用CPTCalendarFormatter而不是CPTTimeFormatter，当您必须设置以秒为单位的时间间隔偏移（例如小时= 60 * 60，日= 24 * 60 * 60）时很好，但几个月的可变天数/秒（30 * 24 * 60 * 60或31 * 24 * 60 * 60,28，闰年等）。 CPTCalendarFormatter允许您为标签上的日期计算确定日历单位。通过这种方式，修复了参考日期和参考日历单位，在数据源方法中，您必须返回从参考日期开始的那些单位的数量。

这里是完整的代码，享受。

在您的viewDidLoad或其他地方在初始化图形：

[...] 

// Graph host view 
CPTGraphHostingView* hostView = [[CPTGraphHostingView alloc] initWithFrame:self.view.frame]; 
[self.view addSubview: hostView]; 

// Your graph 
CPTGraph* graph = [[CPTXYGraph alloc] initWithFrame:hostView.bounds]; 
hostView.hostedGraph = graph; 
CPTXYAxisSet *axisSet = (CPTXYAxisSet *)[graph axisSet];  

// xAxis configuration 
CPTXYAxis *xAxis = [axisSet xAxis]; 
[xAxis setLabelingPolicy:CPTAxisLabelingPolicyFixedInterval]; 
// Prepare dateFormat for current Locale, we want "JAN 2014" "FEB 2014" and so on 
NSString *dateComponents = @"MMMYY"; 
NSString *localDateFormat = [NSDateFormatter dateFormatFromTemplate:dateComponents options:0 locale:[NSLocale currentLocale]]; 
NSDateFormatter *labelDateFormatter=[[NSDateFormatter alloc] init]; 
labelDateFormatter.dateFormat=localDateFormat;  
// Set xAxis date Formatter 
CPTCalendarFormatter *xDateYearFormatter = [[CPTCalendarFormatter alloc] initWithDateFormatter:labelDateFormatter]; 
//Keep in mind this reference date, it will be used to calculate NSNumber in dataSource method 
xDateYearFormatter.referenceDate = [NSDate dateWithTimeIntervalSince1970:0]; 
xDateYearFormatter.referenceCalendarUnit=NSMonthCalendarUnit;  
[xAxis setLabelFormatter:xDateYearFormatter]; 

// yAxis configuration 
CPTXYAxis *yAxis = [axisSet yAxis]; 
[yAxis setMajorIntervalLength:CPTDecimalFromFloat(_YOURYINTERVAL_)]; 
[yAxis setLabelingPolicy:CPTAxisLabelingPolicyFixedInterval]; 
[yAxis setLabelFormatter:_YOURYFORMATTER_]; 
[yAxis setAxisConstraints:[CPTConstraints constraintWithLowerOffset:0.0]] 

// Get the (default) plotspace from the graph so we can set its x/y ranges 
CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *) graph.defaultPlotSpace; 
NSDate *startDate=_YOURSTARTINGDATE_ 
//Number of months since the reference date 
NSInteger xStart=[[[NSCalendar currentCalendar] components: NSCalendarUnitMonth 
           fromDate: xDateYearFormatter.referenceDate 
            toDate: _YOURSTARTINGDATE_ 
            options: 0] month];  
[plotSpace setXRange: [CPTPlotRange plotRangeWithLocation:CPTDecimalFromInteger(xStart)  length:CPTDecimalFromInteger(_YOURDATESARRAY_.count-1)]]; 
[plotSpace setYRange: [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0.0) length:CPTDecimalFromFloat(_YOURMAXYVALUE_)]]; 

[...] 

数据源的方法来对轴返回值：

-(NSNumber *)numberForPlot:(CPTPlot *)plot field:(NSUInteger)fieldEnum recordIndex:(NSUInteger)index 
{ 
    switch (fieldEnum) { 

     case CPTScatterPlotFieldX: { 

      NSInteger monthsOffset=[[[NSCalendar currentCalendar] components: NSCalendarUnitMonth fromDate: [NSDate dateWithTimeIntervalSince1970:0] toDate: [_YOURDATESARRAY_ objectAtIndex:index] options: 0] month];     
      NSNumber *val = [NSNumber numberWithInteger:monthsOffset];  
      return val; 
      break; 
     } 
     case CPTScatterPlotFieldY: { 
      NSNumber *val=_YOURVALUEFORYAXIS_; 
      return val; 
      break; 
     } 
     default: 
      break; 
    } 

    return nil; 
}