Core Plot: Two plots sharing the same x axis

Question

I am trying to set up two charts similar to the AAPlot sample provided with Core Plot. It basically consists of a stock chart, which is shown almost correctly and a second chart (volume chart), which should be placed directly below the stock chart. Both charts should share the same x axis.

Unfortunately the volume chart's data is not being plotted in my app.

Even though I intensely compared the sample source code with mine, I do not find the source of my error.

Could you please point me to right direction?

This is my code:

- (void)configureChart
{
    self.graph = [[CPTXYGraph alloc] initWithFrame:self.hostView.bounds];
    self.hostView.hostedGraph = self.graph;
    self.graph.paddingLeft = 0.0f;
    self.graph.paddingTop = 0.0f;
    self.graph.paddingRight = 0.0f;
    self.graph.paddingBottom = 0.0f;
    self.graph.axisSet = nil;

    // 2 - Set up text style
    CPTMutableTextStyle *textStyle = [CPTMutableTextStyle textStyle];
    textStyle.color = [CPTColor grayColor];
    textStyle.fontName = @"Helvetica-Bold";
    textStyle.fontSize = 16.0f;

    // 3 - Configure title
    NSString *title = self.issue.company.companyName;
    _graph.title = title;    
    _graph.titleTextStyle = textStyle;
    _graph.titlePlotAreaFrameAnchor = CPTRectAnchorTop;    
    _graph.titleDisplacement = CGPointMake(0.0f, -12.0f);      

    // 4 - Set theme
    [self.graph applyTheme:[CPTTheme themeNamed:kCPTStocksTheme]];

    _graph.plotAreaFrame.cornerRadius  = 0.0f;
    CPTMutableLineStyle *borderLineStyle = [CPTMutableLineStyle lineStyle];
    borderLineStyle.lineColor           = [CPTColor whiteColor];
    borderLineStyle.lineWidth           = 2.0f;
    _graph.plotAreaFrame.borderLineStyle = borderLineStyle;


    // Axes
    CPTXYAxisSet *xyAxisSet        = (id)self.graph.axisSet;
    CPTXYAxis *xAxis               = xyAxisSet.xAxis;
    CPTMutableLineStyle *lineStyle = [xAxis.axisLineStyle mutableCopy];
    lineStyle.lineCap   = kCGLineCapButt;
    xAxis.axisLineStyle = lineStyle;
    xAxis.labelingPolicy = CPTAxisLabelingPolicyNone;

    CPTXYAxis *yAxis = xyAxisSet.yAxis;
    yAxis.axisLineStyle = nil;

    // OHLC plot
    CPTMutableLineStyle *whiteLineStyle = [CPTMutableLineStyle lineStyle];
    whiteLineStyle.lineColor = [CPTColor whiteColor];
    whiteLineStyle.lineWidth = 1.0f;
    CPTTradingRangePlot *ohlcPlot = [[CPTTradingRangePlot alloc] initWithFrame:self.graph.bounds];
    ohlcPlot.identifier = @"OHLC";
    ohlcPlot.lineStyle  = whiteLineStyle;
    CPTMutableTextStyle *whiteTextStyle = [CPTMutableTextStyle textStyle];
    whiteTextStyle.color    = [CPTColor whiteColor];
    whiteTextStyle.fontSize = 8.0;
    ohlcPlot.labelTextStyle = whiteTextStyle;
    ohlcPlot.labelOffset    = 5.0;
    ohlcPlot.stickLength    = 2.0f;
    ohlcPlot.dataSource     = self;
    ohlcPlot.plotStyle      = CPTTradingRangePlotStyleOHLC;
    [self.graph addPlot:ohlcPlot];

    // Add volume plot space
    CPTXYPlotSpace *volumePlotSpace = [[CPTXYPlotSpace alloc] init];
    volumePlotSpace.identifier = @"Volume";
    [_graph addPlotSpace:volumePlotSpace];

    CPTBarPlot *volumePlot = [CPTBarPlot tubularBarPlotWithColor:[CPTColor whiteColor] horizontalBars:NO];
    volumePlot.dataSource = self;

    lineStyle            = [volumePlot.lineStyle mutableCopy];
    lineStyle.lineColor  = [CPTColor whiteColor];
    volumePlot.lineStyle = lineStyle;

    volumePlot.fill       = nil;
    volumePlot.barWidth   = CPTDecimalFromFloat(1.0f);
    volumePlot.identifier = @"Volume Plot";
    [_graph addPlot:volumePlot toPlotSpace:volumePlotSpace];


    CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *) self.graph.defaultPlotSpace;
    [plotSpace scaleToFitPlots:[self.graph allPlots]];
}

Answer 1

What happens when you just do [_graph addPlot:volumePlot] instead of [_graph addPlot toPlotSpace:volumePlotSpace]?

I'm thinking that you may have added some extra restraints using all of those various plot spaces and that is keeping both of your plots from showing up.

I'm not entirely sure though to be honest, I've just been learning Core Plot as well, most solutions I've come up are a result of lots of playing around and googling. I'll edit this post if I think of something else.

Answer 2

You never set the plot space ranges for the volume plot space. It still has the default x and y ranges of [0, 1].