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Editorial Team
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Asked: 2026-06-07T08:45:25+00:00

I need to calculate the distance between 2 points on a plot. I am

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I need to calculate the distance between 2 points on a plot.

I am using the method below to achive this need. I tried the others methods but this is the only one that the point is actually plot. On others methods it always return 0.

-(CPTLayer *)dataLabelForPlot:(CPTPlot *)plot recordIndex:(NSUInteger)index 


  NSDecimal plotPoint[2];
        CPTPlotSpace *thePlotSpace = plot.plotSpace;
        CPTPlotArea *thePlotArea   = plot.plotArea;
        CPTCoordinate independentCoord = (NO ? CPTCoordinateY : CPTCoordinateX);

        plotPoint[independentCoord] = [plot cachedDecimalForField:CPTBarPlotFieldBarLocation recordIndex:0];

        CGPoint basePoint;

        basePoint = [plot convertPoint:[thePlotSpace plotAreaViewPointForPlotPoint:plotPoint] fromLayer:thePlotArea];

        plotPoint[independentCoord] = [plot cachedDecimalForField:CPTBarPlotFieldBarLocation recordIndex:1];

        CGPoint basePoint2;

        basePoint2 = [plot convertPoint:[thePlotSpace plotAreaViewPointForPlotPoint:plotPoint] fromLayer:thePlotArea];


        int valor; 
        valor =  basePoint2.x - basePoint.x;

The code above works almost always but i am getting EXC_BAD_ACESS that comes from this code above.

When i comment the code, the exc_bad_acess never occur

Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x00000004
Crashed Thread:  0

Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   Foundation                      0x32f7be56 NSIntegerDivide + 98
1   Foundation                      0x32f7f9e0 NSDecimalDivide + 216
2   InfoTOS007                      0x000e198c CPTDecimalDivide (CPTUtilities.m:496)
3   InfoTOS007                      0x000fd0c8 -[CPTXYPlotSpace     viewCoordinateForViewLength:linearPlotRange:plotCoordinateValue:] (CPTXYPlotSpace.m:384)
4   InfoTOS007                      0x000fd66a -[CPTXYPlotSpace plotAreaViewPointForPlotPoint:] (CPTXYPlotSpace.m:449)
5   InfoTOS007                      0x000bea38 -[GraficoEmbarqueDescarga dataLabelForPlot:recordIndex:] (GraficoEmbarqueDescarga.m:249)
6   InfoTOS007                      0x000ce192 -[CPTPlot relabel] (CPTPlot.m:1016)
7   InfoTOS007                      0x000cb868 -[CPTPlot layoutSublayers] (CPTPlot.m:402)
8   QuartzCore                      0x34272f92 CA::Layer::layout_if_needed(CA::Transaction*) + 210
9   QuartzCore                      0x34277114 CA::Context::commit_transaction(CA::Transaction*) + 220
10  QuartzCore                      0x34276e50 CA::Transaction::commit() + 308
11  QuartzCore                      0x3426ed7e CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 50
12  CoreFoundation                  0x344deb44 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 12
13  CoreFoundation                  0x344dcd80 __CFRunLoopDoObservers + 252
14  CoreFoundation                  0x344dd0da __CFRunLoopRun + 754
15  CoreFoundation                  0x344604d6 CFRunLoopRunSpecific + 294
16  CoreFoundation                  0x3446039e CFRunLoopRunInMode + 98
17  GraphicsServices                0x30d4bfc6 GSEventRunModal + 150
18  UIKit                           0x32a2873c UIApplicationMain + 1084
19  InfoTOS007                      0x000b3468 main (main.m:16)
20  InfoTOS007                      0x000b340c start + 32
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1 Answer

  1. Editorial Team

    It looks like the problem is that your never setting plotPoint[dependentCoord], so it is trying to convert an undefined value to plot coordinates. Just set it to a value within the range of your graph, if all your worried about is the X axis, then the Y axis value doesn’t matter. I haven’t tried compiling the following, but it looks right.

      NSDecimal plotPoint[2];
  CPTPlotSpace *thePlotSpace = plot.plotSpace;
  CPTPlotArea *thePlotArea   = plot.plotArea;
  CPTCoordinate independentCoord =  CPTCoordinateX;
  CPTCoordinate dependentCoord =  CPTCoordinateY;

  plotPoint[independentCoord] = [plot cachedDecimalForField:CPTBarPlotFieldBarLocation recordIndex:0];
  plotPoint[dependentCoord] = CPTDecimalFromInt(1);

  CGPoint basePoint;
  basePoint = [plot convertPoint:[thePlotSpace plotAreaViewPointForPlotPoint:plotPoint] fromLayer:thePlotArea];

  plotPoint[independentCoord] = [plot cachedDecimalForField:CPTBarPlotFieldBarLocation recordIndex:1];
   CGPoint basePoint2;
   basePoint2 = [plot convertPoint:[thePlotSpace plotAreaViewPointForPlotPoint:plotPoint] fromLayer:thePlotArea];

    int valor; 
    valor =  basePoint2.x - basePoint.x;
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