Why won't my x-axis show with core-plot on the iPhone?

Question

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;                 

}

Answer 1

I've had the same problem yesterday/today and the solution seems to be using the orthogonalCoordinateDecimal property on the axis. For example:

graph.axisSet.xAxis.orthogonalCoordinateDecimal = CPDecimalFromFloat(minHeight);

Answer 2

You set the position of an axis on the orthogonal axis using the constantCoordinateValue property of the axis. Just set that property on the x axis to a positive value of y, and the axis should move up.

Answer 3

https://github.com/djw/core-plot/tree/9282845bddbb8c40ff314bbfa158beff797c91f7/examples

This states that the isFloatingAxis property has been removed from at least version 0.9.

I also found this in the discussion group as well http://code.google.com/p/core-plot/issues/detail?id=125

After some hunting, it looks like the new way to float an axis looks like this:

x.axisConstraints = [CPTConstraints constraintWithUpperOffset:132];

Answer 4

this framework really needs a better way to configure itself. I don't see any problem jumping out. Maybe just try simplifying the method to the point where debugging becomes manageable. Check the data that you are passing in to make sure it is what you expect it to be. Better yet, create some dummy data that you know will produce the plot you expect.