xcode – 核心图中的两个y轴,具有不同的轴刻度

我正在编写一个应用程序,其中我有两个y轴和一个x轴的图形.左侧y轴的范围从0到20所以有20个majorTick轴.右y轴的范围从0到10,所以我想要左y轴标记为每个替代majorTickAxis.

这是我的代码片段

//code
   CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)self.graph.defaultPlotSpace;
float xmax=10.0;
float xmin=0.0;
plotSpace.xrange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(xmin)      length:CPTDecimalFromFloat(xmax-xmin)];
float ymax=20.0;
float ymin=0.0;
float ymax2=10.0;
plotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(ymin) length:CPTDecimalFromFloat(ymax-ymin)];



// Grid line styles
CPTMutableLinestyle *majorGridLinestyle = [CPTMutableLinestyle linestyle];
majorGridLinestyle.linewidth = 0.75;
majorGridLinestyle.lineColor = [[CPTColor whiteColor] colorWithAlphaComponent:0.75];

CPTMutableLinestyle *minorGridLinestyle = [CPTMutableLinestyle linestyle];
minorGridLinestyle.linewidth = 0.25;
minorGridLinestyle.lineColor = [[CPTColor whiteColor] colorWithAlphaComponent:0.1];

CPTMutableLinestyle *redLinestyle = [CPTMutableLinestyle linestyle];
redLinestyle.linewidth = 2.0;
redLinestyle.lineColor = [[CPTColor redColor] colorWithAlphaComponent:0.5];                         

CPTMutableLinestyle *greenLinestyle = [CPTMutableLinestyle linestyle];
greenLinestyle.linewidth = 2.0;
greenLinestyle.lineColor = [[CPTColor greenColor] colorWithAlphaComponent:0.5];     

// Axes
CPTXYAxisSet *axisSet = (CPTXYAxisSet *)self.graph.axisSet;
CPTXYAxis *x          = axisSet.xAxis;
x.orthogonalCoordinateDecimal = CPTDecimalFromString(@"0");
x.majorIntervalLength = [[NSDecimalNumber decimalNumberWithString:@"1"] decimalValue];
x.minorTicksPerInterval       = 4;
x.labelOffset = 3.0f;
x.title         = @"Time";
x.titleOffset   = 20.0;
x.titleLocation = CPTDecimalFromFloat((xmax+xmin)/2);
x.majorGridLinestyle= majorGridLinestyle;
x.minorGridLinestyle=minorGridLinestyle;


CPTXYAxis *y = axisSet.yAxis;
y.majorIntervalLength         = CPTDecimalFromString(@"1.0");
y.majorTickLength=2.0f;
y.minorTicksPerInterval       = 4;
y.orthogonalCoordinateDecimal = CPTDecimalFromFloat(0.0);
y.labelExclusionRanges = [NSArray arrayWithObjects:
                          [CPTPlotRange plotRangeWithLocation:CPTDecimalFromInteger(0.0) 
                                                       length:CPTDecimalFromInteger(0.0)],Nil];
y.majorGridLinestyle= majorGridLinestyle;
y.minorGridLinestyle=minorGridLinestyle;


CPTXYAxis *y2 = [[(CPTXYAxis *)[CPTXYAxis alloc] initWithFrame:CGRectZero] autorelease];
y2.plotSpace    =plotSpace;     
y2.orthogonalCoordinateDecimal = CPTDecimalFromFloat(xmax);
y2.majorGridLinestyle=majorGridLinestyle;
y2.minorGridLinestyle=minorGridLinestyle;
y2.minorTicksPerInterval       = 4;
y2.majorIntervalLength        = CPTDecimalFromString(@"1.0");
y2.labelOffset        = 10.0;
y2.coordinate          =CPTCoordinateY;

y2.axisLinestyle       = x.axisLinestyle;
y2.labelTextStyle              = x.labelTextStyle;
y2.labelOffset                 = -30.0f;
y2.visibleRange                = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromInteger(0) length:CPTDecimalFromInteger(ymax2)];


y2.title                       = @"Temperature";
y2.titleLocation               = CPTDecimalFromInteger(5.0);
y2.titleTextStyle              =x.titleTextStyle;
y2.titleOffset                 =-45.0f;
y2.labelExclusionRanges = [NSArray arrayWithObjects:
                          [CPTPlotRange plotRangeWithLocation:CPTDecimalFromInteger(0.0) 
                                                       length:CPTDecimalFromInteger(0.0)],Nil];


self.graph.axisSet.axes = [NSArray arrayWithObjects:x,y,y2,nil];

// Create a plot that uses the data source method for red graph
CPTScatterPlot *redplot = [[[CPTScatterPlot alloc] init] autorelease];
redplot.identifier = @"red Plot";;

CPTMutableLinestyle *linestyle = [[redplot.dataLinestyle mutablecopy] autorelease];
linestyle.miterLimit        = 1.0f;
redplot.dataLinestyle = redLinestyle;
redplot.dataSource = self;
redplot.interpolation = CPTScatterPlotInterpolationStepped;

[self.graph addplot:redplot];

// Create a plot that uses the data source method for green graph
CPTScatterPlot *greenPlot = [[[CPTScatterPlot alloc] init] autorelease];
greenPlot.identifier = @"green Plot";;

CPTMutableLinestyle *greenlinestyle = [[greenPlot.dataLinestyle mutablecopy] autorelease];
greenlinestyle.miterLimit       = 1.0f;
greenPlot.dataLinestyle = greenLinestyle;
greenPlot.dataSource = self;
[self.graph addplot:greenPlot];

 // Add some data
NSMutableArray *newData = [NSMutableArray arrayWithCapacity:100];
NSUInteger i;
for ( i = 0; i < 45; i++ ) {
    id x = [NSNumber numberWithDouble:i * 0.2];
    id y = [NSNumber numberWithDouble:i * rand() / ((double)RAND_MAX*5.0) ];        
    [newData addobject:[NSDictionary dictionaryWithObjectsAndKeys:
      x,@"x",@"y",nil]];
}
NSMutableArray *newData1 = [NSMutableArray arrayWithCapacity:100];
for ( i = 0; i < 45; i++ ) {
    id x =[NSNumber numberWithDouble:i * rand() / ((double)RAND_MAX*5.0) ]; 
    id y2 = [NSNumber numberWithDouble:i * 0.2];
    [newData1 addobject:[NSDictionary dictionaryWithObjectsAndKeys:
                        x,@"y2",nil]];
}
self.plotData = newData;
self.plotData2=newData1;

解决方法

如果希望两个y轴具有不同的比例,则需要添加另一个绘图空间.对第二个绘图空间使用相同的xrange,但使用不同的yRange,例如,

CPTXYPlotSpace *plotSpace2 = [[[CPTXYPlotSpace alloc] init] autorelease];
plotSpace2.xrange = plotSpace.xrange;
plotSpace2.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(ymin)
                                                 length:CPTDecimalFromFloat(ymax2 - ymin)];
[graph addplotSpace:plotSpace2];
y2.plotSpace = plotSpace2;

使用majorIntervalLength来控制刻度线和网格线的位置：

y.majorIntervalLength = CPTDecimalFromFloat((ymax - ymin) / 10.0f);
y2.majorIntervalLength = CPTDecimalFromFloat((ymax2 - ymin) / 10.0f);