Questions about scatter plot in Core Plot - ios

Question

I am making a scatter plot app in Core Plot 1.4. I am new to Objective-C and Core Plot, so sorry for asking some basic questions. Here is some code I wrote by imitating the sample program(CPTTestApp-iphone).
- (void)viewDidLoad
{
[super viewDidLoad];
...
// Add some initial data
NSMutableArray *contentArray = [NSMutableArray arrayWithCapacity:100];
int i;
for ( i = 0; i < 60; i++ ) {
id x = [NSNumber numberWithFloat:1 + i * 0.05];
id y = [NSNumber numberWithInt:1]; //[NSNumber numberWithFloat:1.2 * rand() / (float)RAND_MAX + 1.2];
[contentArray addObject:[NSMutableDictionary dictionaryWithObjectsAndKeys:x, #"x", y, #"y", nil]];
}
dataForPlot = contentArray;
// Create graph from theme
graph = [[CPTXYGraph alloc] initWithFrame:CGRectZero];
CPTTheme *theme = [CPTTheme themeNamed:kCPTDarkGradientTheme];
[graph applyTheme:theme];
CPTGraphHostingView *hostingView = [[CPTGraphHostingView alloc] init];
hostingView.collapsesLayers = NO; // Setting to YES reduces GPU memory usage, but can slow drawing/scrolling
hostingView.hostedGraph = graph;
[self setView:hostingView];
graph.paddingLeft = 0.0;
graph.paddingTop = 0.0;
graph.paddingRight = 0.0;
graph.paddingBottom = 30.0;
// Setup plot space
CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)graph.defaultPlotSpace;
plotSpace.allowsUserInteraction = YES;
[plotSpace setXRange:[CPTPlotRange plotRangeWithLocation:CPTDecimalFromInteger(0) length:CPTDecimalFromInteger(5)]];
[plotSpace setYRange:[CPTPlotRange plotRangeWithLocation:CPTDecimalFromInteger(0) length:CPTDecimalFromInteger(7)]];
// Axes
CPTXYAxisSet *axisSet = (CPTXYAxisSet *)graph.axisSet;
CPTXYAxis *x = axisSet.xAxis;
x.majorIntervalLength = CPTDecimalFromString(#"1");
x.orthogonalCoordinateDecimal = CPTDecimalFromString(#"0");
x.minorTicksPerInterval = 5;
NSArray *exclusionRanges = [NSArray arrayWithObjects:
[CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(1.99) length:CPTDecimalFromFloat(0.02)],
[CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0.99) length:CPTDecimalFromFloat(0.02)],
[CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(2.99) length:CPTDecimalFromFloat(0.02)],
nil];
x.labelExclusionRanges = exclusionRanges;
CPTXYAxis *y = axisSet.yAxis;
y.majorIntervalLength = CPTDecimalFromString(#"1");
y.minorTicksPerInterval = 5;
y.orthogonalCoordinateDecimal = CPTDecimalFromString(#"0");
exclusionRanges = [NSArray arrayWithObjects:
[CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(1.99) length:CPTDecimalFromFloat(0.02)],
[CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0.99) length:CPTDecimalFromFloat(0.02)],
[CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(3.99) length:CPTDecimalFromFloat(0.02)],
nil];
y.labelExclusionRanges = exclusionRanges;
y.delegate = self;
// Create a blue plot area
CPTScatterPlot *boundLinePlot = [[CPTScatterPlot alloc] init];
CPTMutableLineStyle *lineStyle = [CPTMutableLineStyle lineStyle];
lineStyle.miterLimit = 1.0f;
lineStyle.lineWidth = 3.0f;
lineStyle.lineColor = [CPTColor blueColor];
boundLinePlot.dataLineStyle = lineStyle;
boundLinePlot.identifier = #"Blue Plot";
boundLinePlot.dataSource = self;
[graph addPlot:boundLinePlot toPlotSpace:plotSpace];
// Do a blue gradient
CPTColor *areaColor1 = [CPTColor colorWithComponentRed:0.3 green:0.3 blue:1.0 alpha:0.8];
CPTGradient *areaGradient1 = [CPTGradient gradientWithBeginningColor:areaColor1 endingColor:[CPTColor clearColor]];
areaGradient1.angle = -90.0f;
CPTFill *areaGradientFill = [CPTFill fillWithGradient:areaGradient1];
boundLinePlot.areaFill = areaGradientFill;
boundLinePlot.areaBaseValue = [[NSDecimalNumber zero] decimalValue];
// interpolation
boundLinePlot.interpolation = CPTScatterPlotInterpolationCurved;
#ifdef PERFORMANCE_TEST
[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:#selector(changePlotRange) userInfo:nil repeats:YES];
#endif
}
Now I have some questions.
From dataForPlot, a blue line with gradient must be rendered the height y=1, but after running this it was not shown. (I haven't adjust the range of x values in dataForPlot but a partial line should be rendered.)
How can I move the origin (0,0) to the middle of the screen?
Why do 1.0-3.0 in x-axis and 1.0, 2.0, 4.0 in y-axis disappear?
Can anyone help me figure these out? Thank you.

Answer 1

What data is being plotted? Please show the datasource methods.
The visible data ranges in the plot area are controlled by the plot space:
plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromInteger(-5)
length:CPTDecimalFromInteger(10)];
plotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromInteger(-7)
length:CPTDecimalFromInteger(14)];
The labelExclusionRanges skips over any labels in the specified ranges. If you want to see all of the ticks and labels, don't set this property.