Two y axis in core plot graph with different axis scales

core-plot, xcode

Solution

If you want the two y-axes to have different scales, you need to add another plot space. Use the same `xRange` for the second plot space, but use a different `yRange`, e.g.,

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;

Use the `majorIntervalLength` to control the location of the ticks and grid lines:

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

Problem

I am programming a app where I have graph with two y axis and one x axis.left y axis has range from 0 to 20 so there are 20 majorTick axis.Right y axis has range from 0 to 10,so I want left y axis to be labelled for every alternate majorTickAxis. here is my code snippet ``` //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, @"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, @"x",y2, @"y2",nil]]; } self.plotData = newData; self.plotData2=newData1; ```

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