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Editorial Team
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Asked: 2026-05-30T19:51:23+00:00

Problem I am drawing a bar chart with Core Plot . My implementation of

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Problem

I am drawing a bar chart with Core Plot. My implementation of the numberForPlot as the data source seems to return the values correctly. However, depending on the setting of barPlot.Offset the chart starts with the wrong value.

Datasource implementation

I have implemented the datasource as follows:

- (NSArray *)numbersForPlot:(CPTPlot *)plot 
                 field:(NSUInteger)fieldEnum 
      recordIndexRange:(NSRange)indexRange; 

if(fieldEnum == 3) {

NSString *coa = [[NSString alloc] init];
coa = (NSString*)[plot identifier];

NSMutableArray *values = [[NSMutableArray alloc] init] ;
for (IBFinPeriod *fp in periodsArray) {
    NSNumber *value = [self.company valueForCoa:coa FiscalYear:[fp FiscalYear] FiscalPeriod:[fp FiscalPeriod]];
    [values addObject:value];
    }
NSLog(@"plot values: %@",values);
return values;

}
else

    return    [[NSArray alloc]initWithObjects:[NSDecimalNumber numberWithFloat:1.0],
               [NSDecimalNumber numberWithFloat:2.0],
               [NSDecimalNumber numberWithFloat:3.0],
               [NSDecimalNumber numberWithFloat:4.0],
               [NSDecimalNumber numberWithFloat:5.0],
               nil]; 
}

This code returns the y-values: “1841.059”,
“2492.619”,
“3011.582”,
“2643.865”,
“2914.845”,
“3470.457”, which is correct.

Barplot offset

However, only when barPlot.barOffset = CPTDecimalFromFloat(-0.50f);
 the plot starts correctly with the first value on the left.

chart with barPlot.offset = -0.50f

If barPlot.barOffset
is set to 0, it starts with the left half of the last value (3470.57):

chart with barPlot.offset = 0.00f

Chart set-up

This is the code to set-up the chart:

- (void) setChart;

{
graph1 = [[CPTXYGraph alloc] initWithFrame: self.view.bounds];

CPTTheme *theme = [CPTTheme themeNamed:kCPTPlainWhiteTheme];
[graph1 applyTheme:theme];
self.chartLeft.hostedGraph = graph1;
graph1.plotAreaFrame.masksToBorder = NO;


// Border
graph1.plotAreaFrame.borderLineStyle = nil;
graph1.plotAreaFrame.cornerRadius = 5.0f;

// Paddings
graph1.paddingLeft  = 10.0;
graph1.paddingTop   = 10.0;
graph1.paddingRight = 10.0;
graph1.paddingBottom = 10.0;

graph1.plotAreaFrame.paddingLeft = 50.0;
graph1.plotAreaFrame.paddingTop = 20.0;
graph1.plotAreaFrame.paddingRight = 20.0;
graph1.plotAreaFrame.paddingBottom = 50.0;
graph1.plotAreaFrame.backgroundColor = nil;

graph1.paddingLeft = 20.0;
graph1.paddingTop = 20.0;
graph1.paddingRight = 20.0;
graph1.paddingBottom = 20.0;

// Setup plot space
// The plot space determines the data ranges that are visible in the graph, not its physical size in the view
CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)graph1.defaultPlotSpace;
plotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0.0f) length:CPTDecimalFromFloat(4000.0f)];
plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0.0f) length:CPTDecimalFromFloat(5.0f)];

CPTXYAxisSet *axisSet = (CPTXYAxisSet *)graph1.axisSet;
CPTXYAxis *x          = axisSet.xAxis;
x.axisLineStyle               = nil;
x.majorTickLineStyle          = nil;
x.minorTickLineStyle          = nil;
x.majorIntervalLength         = CPTDecimalFromString(@"1");
x.orthogonalCoordinateDecimal = CPTDecimalFromString(@"0");
x.title                       = @"X Axis";
x.titleLocation               = CPTDecimalFromFloat(7.5f);
x.titleOffset                 = 55.0f;

// Custom labels omitted...

CPTXYAxis *y = axisSet.yAxis;
y.axisLineStyle               = nil;
y.majorTickLineStyle          = nil;
y.minorTickLineStyle          = nil;
y.majorIntervalLength         = CPTDecimalFromString(@"1000");
y.orthogonalCoordinateDecimal = CPTDecimalFromString(@"0");
y.title                       = @"Y Axis";
y.titleOffset                 = 45.0f;
y.titleLocation               = CPTDecimalFromFloat(150.0f);

// First bar plot
CPTBarPlot *barPlot = [CPTBarPlot tubularBarPlotWithColor:[CPTColor darkGrayColor] horizontalBars:NO];
barPlot.baseValue  = CPTDecimalFromString(@"0");
barPlot.barOffset  = CPTDecimalFromFloat(-0.50f);
barPlot.identifier = @"SOPI";
barPlot.dataSource = self;
[graph1 addPlot:barPlot toPlotSpace:plotSpace];

}

Question

What is wrong with my implementation?

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1 Answer

  1. Editorial Team

    I found the solution to my problem:

    My return statement for the x values was missing numberWithFloat 6.0

    return    [[NSArray alloc]initWithObjects:[NSDecimalNumber numberWithFloat:1.0],
           [NSDecimalNumber numberWithFloat:2.0],
           [NSDecimalNumber numberWithFloat:3.0],
           [NSDecimalNumber numberWithFloat:4.0],
           [NSDecimalNumber numberWithFloat:5.0],
           nil];

    In addition, the length in plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0.0f) length:CPTDecimalFromFloat(5.0f)]was only 5. However, I have 6 x-values. I have set the length to 6.5 now. However, when setting it to 6.0, the right bar is shown

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