EDIT: I think my question is better phrased as: How can I have a Y-axis that doesn't start at zero? It seems like the x-axis always gets placed at the y=0, but I would like the x-axis to be at some positive number on the y-axis.
Here's a graph with more regular data... I just wish the x-axis was placed at the minimum y-value for the plot (about 77), instead of at 0.
Here is the function I use to create the graph.
It's a whole bunch of code, and I'm not quite sure which piece might be off to not display the x-axis.
Could the x-axis not showing have something to do with my data?
- (void) showGraph:(SavedDetailScreen*)dataSource {
// create the graph and add it to the view
CPXYGraph *graph = [[CPXYGraph alloc] initWithFrame: CGRectZero];
graph.plotArea.masksToBorder = NO;
CPLayerHostingView *graphView = [[CPLayerHostingView alloc] initWithFrame:CGRectMake(0,0, 280, 240)];
[self addSubview:graphView];
graphView.hostedLayer = graph;
graph.paddingLeft = 50.0;
graph.paddingTop = 20.0;
graph.paddingRight = 10.0;
graph.paddingBottom = 40.0;
// set up the ranges for the graph axis
float minElevation = dataSource.track.tbStats.minAlt;
float maxElevation = dataSource.track.tbStats.maxAlt-dataSource.track.tbStats.minAlt;
float minDistance = 0.0f;
float maxDistance = dataSource.track.tbStats.totalDistance;
CPXYPlotSpace *plotSpace = (CPXYPlotSpace *)graph.defaultPlotSpace;
plotSpace.xRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(minDistance)
length:CPDecimalFromFloat(maxDistance)];
plotSpace.yRange = [CPPlotRange plotRangeWithLocation:CPDecimalFromFloat(minElevation)
length:CPDecimalFromFloat(maxElevation)];
// style the graph with white text and lines
CPTextStyle *whiteText = [CPTextStyle textStyle];
whiteText.color = [CPColor whiteColor];
CPLineStyle *whiteStyle = [CPLineStyle lineStyle];
whiteStyle.lineColor = [CPColor whiteColor];
whiteStyle.lineWidth = 2.0f;
// set up the axis
CPXYAxisSet *axisSet = (CPXYAxisSet *)graph.axisSet;
CPXYAxis *x = axisSet.xAxis;
CPXYAxis *y = axisSet.yAxis;
x.majorIntervalLength = CPDecimalFromFloat(maxDistance/10.0f);
x.minorTicksPerInterval = 0;
x.majorTickLineStyle = whiteStyle;
x.minorTickLineStyle = whiteStyle;
x.axisLineStyle = whiteStyle;
x.minorTickLength = 5.0f;
x.majorTickLength = 10.0f;
x.labelOffset = 3.0f;
x.labelTextStyle = whiteText;
y.majorIntervalLength = CPDecimalFromFloat(maxElevation/5.0f);
y.minorTicksPerInterval = 0;
y.majorTickLineStyle = whiteStyle;
y.minorTickLineStyle = whiteStyle;
y.axisLineStyle = whiteStyle;
y.minorTickLength = 5.0f;
y.majorTickLength = 10.0f;
y.labelOffset = 3.0f;
y.labelTextStyle = whiteText;
CPScatterPlot *plot = [[[CPScatterPlot alloc] initWithFrame:graph.bounds] autorelease];
plot.dataLineStyle.lineWidth = 2.0f;
plot.dataLineStyle.lineColor = [CPColor blueColor];
plot.dataSource = dataSource;
[graph addPlot:plot];
CPPlotSymbol *greenCirclePlotSymbol = [CPPlotSymbol ellipsePlotSymbol];
greenCirclePlotSymbol.fill = [CPFill fillWithColor:[CPColor greenColor]];
greenCirclePlotSymbol.size = CGSizeMake(2.0, 2.0);
plot.plotSymbol = greenCirclePlotSymbol;
}