Question

在散点图上，我的x坐标数据只是表示自纪元以来的秒数的长数字，而y坐标数据如下所示：0.675088,0.670629,0.6669599。我希望在y轴上显示为主要刻度的是这样的：0.64,0.65,0.66,0.67但是图表上当前显示的是：0.5,0.7,1.0,1.2。

首先，我不知道为什么我会得到如上所述的不规则蜱间隔（0.5到0.7 = 0.2,0.7到1.0 = 0.3？）但我猜是因为我正在试验标签政策并将其设置为CPTAxisLabelingPolicyEqualDivisions - 有人可以解释所有这些标签政策的含义吗？

真正的问题是，考虑到我正在绘制非常小的数字，我应该在y轴上使用majorIntervalLength的值是什么？目前我有0.01但是当我按-n的数量级调整这个值时，它实际上对我的图表没有任何影响。

这是我的代码片段基于Plot_Gallery_iOS DatePlot.m

-(void)renderInLayer:(CPTGraphHostingView *)layerHostingView withTheme:(CPTTheme *)theme
{
CGRect bounds = layerHostingView.bounds;

NSDate *refDate = [NSDate dateWithTimeIntervalSince1970:0];
NSTimeInterval oneDay = 24 * 60 * 60;

CPTGraph *graph = [[[CPTXYGraph alloc] initWithFrame:bounds] autorelease];
[self addGraph:graph toHostingView:layerHostingView];
[self applyTheme:theme toGraph:graph withDefault:[CPTTheme themeNamed:kCPTPlainWhiteTheme]];

[self setTitleDefaultsForGraph:graph withBounds:bounds];
[self setPaddingDefaultsForGraph:graph withBounds:bounds];

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

NSTimeInterval now = [[NSDate date] timeIntervalSince1970];
NSTimeInterval threeMonthsago = now - (90*oneDay);

plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(threeMonthsago) length:CPTDecimalFromFloat(now - threeMonthsago)];
plotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0.6f) length:CPTDecimalFromFloat(0.7f)];

NSDateFormatter *dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
dateFormatter.dateStyle = kCFDateFormatterShortStyle;
CPTTimeFormatter *timeFormatter = [[[CPTTimeFormatter alloc] initWithDateFormatter:dateFormatter] autorelease];
timeFormatter.referenceDate = refDate;

// Axes
CPTXYAxisSet *axisSet = (CPTXYAxisSet *)graph.axisSet;
CPTXYAxis *x          = axisSet.xAxis;
x.majorIntervalLength         = CPTDecimalFromFloat(oneDay*30);
x.orthogonalCoordinateDecimal = CPTDecimalFromFloat(0.6f);
x.minorTicksPerInterval       = 7;
x.labelFormatter            = timeFormatter;
x.labelRotation             = M_PI / 4;
x.preferredNumberOfMajorTicks = 5;

CPTXYAxis *y = axisSet.yAxis;
y.majorIntervalLength         = CPTDecimalFromDouble(0.001);
y.labelingPolicy = CPTAxisLabelingPolicyEqualDivisions;
y.preferredNumberOfMajorTicks = 5;
y.minorTicksPerInterval       = 10;
y.orthogonalCoordinateDecimal = CPTDecimalFromFloat(now);
//    y.visibleRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0.6f) length:CPTDecimalFromFloat(0.1f)];
CPTScatterPlot *dataSourceLinePlot = [[[CPTScatterPlot alloc] init] autorelease];
dataSourceLinePlot.identifier = @"Date Plot";

// [plotSpace scaleToFitPlots:[NSArray arrayWithObjects:dataSourceLinePlot, nil]];

CPTMutableLineStyle *lineStyle = [[dataSourceLinePlot.dataLineStyle mutableCopy] autorelease];
lineStyle.lineWidth              = .5f;
lineStyle.lineColor              = [CPTColor greenColor];
dataSourceLinePlot.dataLineStyle = lineStyle;

// Auto scale the plot space to fit the plot data
// Extend the ranges by 30% for neatness
[plotSpace scaleToFitPlots:[NSArray arrayWithObjects:dataSourceLinePlot, nil]];
CPTMutablePlotRange *xRange = [[plotSpace.xRange mutableCopy] autorelease];
CPTMutablePlotRange *yRange = [[plotSpace.yRange mutableCopy] autorelease];
[xRange expandRangeByFactor:CPTDecimalFromDouble(1.3)];
[yRange expandRangeByFactor:CPTDecimalFromDouble(1.3)];
plotSpace.xRange = xRange;
plotSpace.yRange = yRange;

dataSourceLinePlot.dataSource = self;
[graph addPlot:dataSourceLinePlot];
 }

更新：

通过这样设置自定义y主要滴答来解决问题：

y.labelingPolicy = CPTAxisLabelingPolicyLocationsProvided;

NSSet *majorTickLoc = [NSSet setWithObjects:[NSDecimalNumber numberWithFloat:0.64f], [NSDecimalNumber numberWithFloat:0.65f], [NSDecimalNumber numberWithFloat:0.66f], [NSDecimalNumber numberWithFloat:0.67f],[NSDecimalNumber numberWithFloat:0.68f],nil];
y.majorTickLocations = majorTickLoc;

但这个数字似乎仍然是四舍五入的，即只有一个分数位数为0.6,0.7,0.7等，结果证明这只是标签。设置标签上的数字格式器：

NSNumberFormatter *yFormatter = [[NSNumberFormatter alloc] init];
[yFormatter setMinimumFractionDigits:4];
[yFormatter setMaximumFractionDigits:4];
[yFormatter setNumberStyle:NSNumberFormatterDecimalStyle];
y.labelFormatter = yFormatter;

Answer 1

请尝试以下代码：

y.majorIntervalLength = CPTDecimalFromString(@"0.1")

Answer 2

为y轴设置labelFormatter。

NSNumberFormatter *newFormatter = [[[NSNumberFormatter alloc] init] autorelease];
newFormatter.minimumIntegerDigits = 1;
newFormatter.maximumFractionDigits = 2;
newFormatter.minimumFractionDigits = 2;
y.labelFormatter = newFormatter;

核心图 - 在散点图上绘制非常小的数字

2 个答案: