Core plot majorIntervalLength : unable to make it work - iphone

Question

am trying to plot a simple graph (cannot be so tough! I have used core plot successfully before!). I have some dates to be plotted in the x-axis. And some small float values in the y-axis, like 0.139503, 0.139481, etc. I have to plot 5 such values (which I fetch from the backend).
For the y-axis range, am finding the lowest of these values and setting it as the start of the y-axis range. And am setting the majorIntervalLength to (highestValue - LowestValue)/5, which is (for example) 0.007946. But the y-axis interval seems to be fixed at interval of 1. So, since my y-axis values are really small (difference between them is in the order of 0.01), all plots are being drawn at y=0.0. Here's the code snippet :
-(void) initializeGraph {
if ((self.graph == nil) || (self.graph == NULL)) {
self.graphHostView = [(CPTGraphHostingView *) [CPTGraphHostingView alloc] initWithFrame:self.view.bounds];
self.graph = [[CPTXYGraph alloc] initWithFrame:self.graphHostView.bounds];
graph.paddingLeft = 2.0;
graph.paddingRight = 2.0;
graph.paddingTop = 2.0;
graph.paddingBottom = 2.0;
graph.title = #"Graph Plot";
// plotting style is set to line plots
CPTMutableLineStyle *lineStyle = [CPTMutableLineStyle lineStyle];
lineStyle.lineColor = [CPTColor blackColor];
lineStyle.lineWidth = 2.0f;
CPTXYAxisSet *axisSet = (CPTXYAxisSet *) self.graph.axisSet;
axisSet.xAxis.majorTickLineStyle = lineStyle;
axisSet.xAxis.majorTickLength = 7.0f;
axisSet.xAxis.labelingPolicy = CPTAxisLabelingPolicyEqualDivisions;
axisSet.yAxis.labelingPolicy = CPTAxisLabelingPolicyEqualDivisions;
axisSet.xAxis.labelRotation = 90.0;
CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *) self.graph.defaultPlotSpace;
// Determine the lowest and highest values to be plotted in Y Axis)
CGFloat yLow = 0.1;
CGFloat yHigh = yLow;
for (int i=0 ; i<self.dict.count ; i++) {
MyCustomObject *myData = (MyCustomObject *) [dict objectForKey:
[self.arrayKeys objectAtIndex:i]];
if (myData.mem < yLow) {
yLow = myData.mem;
}
if (yHigh < myData.mem) {
yHigh = myData.mem;
}
}
plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0)
length:CPTDecimalFromFloat(5)];
plotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(yLow)
length:CPTDecimalFromFloat(5)];
// To determine the point where your graph starts
//axisSet.yAxis.orthogonalCoordinateDecimal = CPTDecimalFromFloat(yLow);
axisSet.yAxis.majorIntervalLength = CPTDecimalFromCGFloat((yHigh-yLow)/5.0);
NSLog(#"Y axis interval : %f", (yHigh-yLow)/5.0);
...
}
-(NSNumber *) numberForPlot:(CPTPlot *)plot
field:(NSUInteger)fieldEnum
recordIndex:(NSUInteger)index {
if ( fieldEnum == CPTScatterPlotFieldY ) {
return [NSNumber numberWithFloat:myData.mem];
} else {
return [NSNumber numberWithInt:index];
}
}
Why is that the majorIntervalLength for y axis that am setting not working?

Answer 1

are you setting the axisSet.yAxis.majorTickLength anywhere? i don't see it in your code above.
if the majorTickLength is nil nothing will show up for the tick's.

Answer 2

Setting length of yRange (as Erik Skroch suggested) to (yHigh-yLow) helped