Question

I am working with the core-plot framework to create a bar graph with a legend. It all works except that the legend is duplicating the the columns in each section of the bar graph (Please see attached screen shot).

I have looked through the core-plot class reference and was not able to find anything to fix this problem. I have tried to set the CPTLegend properties numberOfColumns to 1 and the numberOfRows to 3 and that made the legend display the appropriate amount of items in the legend, but the data it was displaying was not correct.

Below is the code I’m using to build the bar graph. Do you all have any suggestions how I can fix this issue? I am assuming this is not so much a bug with core-plot but a limitation of the legend and am hoping there is a workaround.

// Create barChart from theme
barChart = [[CPTXYGraph alloc] initWithFrame:CGRectZero];
CPTTheme *theme = [CPTTheme themeNamed:kCPTDarkGradientTheme];
[barChart applyTheme:theme];
chartView.hostedGraph = barChart;
barChart.plotAreaFrame.masksToBorder = NO;

barChart.paddingLeft = 60.0;
barChart.paddingTop = 10.0;
barChart.paddingRight = 0.0;
barChart.paddingBottom = 30.0;

//find max y
int maxY = 0;
NSMutableArray *maxDrillDownData = [chartData.drillDownData objectForKey:DRILLDOWN_EQUIPMENT_ALL_TYPE];
for (NSMutableArray *dataArray in maxDrillDownData) {
    maxY = dataArray.count>maxY?dataArray.count:maxY;
}

//add buffer
maxY = maxY+100;

// Add plot space for horizontal bar charts
CPTXYPlotSpace *plotSpace = (CPTXYPlotSpace *)barChart.defaultPlotSpace;
plotSpace.yRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0.0f) length:CPTDecimalFromInt(maxY)];
plotSpace.xRange = [CPTPlotRange plotRangeWithLocation:CPTDecimalFromFloat(0.0f) length:CPTDecimalFromFloat(3.25)];

CPTXYAxisSet *axisSet = (CPTXYAxisSet *)barChart.axisSet;
CPTXYAxis *x = axisSet.xAxis;
x.axisLineStyle = nil;
x.majorTickLineStyle = nil;
x.minorTickLineStyle = nil;
x.majorIntervalLength = CPTDecimalFromString(@"1");
x.orthogonalCoordinateDecimal = CPTDecimalFromString(@"0");
x.titleLocation = CPTDecimalFromFloat(7.5f);
x.titleOffset = 55.0f;
x.labelOffset = 2.0;

// Define some custom labels for the data elements
x.labelRotation = M_PI/4;
x.labelingPolicy = CPTAxisLabelingPolicyNone;
NSArray *customTickLocations = [NSArray arrayWithObjects:[NSDecimalNumber numberWithFloat:0.5], [NSDecimalNumber numberWithFloat:1.5], [NSDecimalNumber numberWithFloat:2.5], nil];
NSArray *xAxisLabels = (NSMutableArray *)[chartData.labels objectForKey:LABELS_EQUIPMENT_TYPE];
NSUInteger labelLocation = 0;
NSMutableArray *customLabels = [NSMutableArray arrayWithCapacity:[xAxisLabels count]];
for (NSNumber *tickLocation in customTickLocations) {
    CPTAxisLabel *newLabel = [[CPTAxisLabel alloc] initWithText: [xAxisLabels objectAtIndex:labelLocation++] textStyle:x.labelTextStyle];
    newLabel.tickLocation = [tickLocation decimalValue];
    newLabel.offset = x.labelOffset;
    [customLabels addObject:newLabel];
    //[newLabel release];
}

x.axisLabels =  [NSSet setWithArray:customLabels];

CPTXYAxis *y = axisSet.yAxis;
y.axisLineStyle = nil;
y.majorTickLineStyle = nil;
y.minorTickLineStyle = nil;
y.majorIntervalLength = CPTDecimalFromString(@"50");
y.orthogonalCoordinateDecimal = CPTDecimalFromString(@"0");
y.title = (NSString *)[chartData.labels objectForKey:LABELS_Y_AXIS];
y.titleOffset = 45.0f;
y.titleLocation = CPTDecimalFromFloat(150.0f);

//identifiers
NSMutableArray *identifiers = (NSMutableArray *)[chartData.identifiers objectForKey:IDENTIFIER_EQUIPMENT_TYPE];

// First bar plot
CPTBarPlot *barPlot = [CPTBarPlot tubularBarPlotWithColor:[CPTColor darkGrayColor] horizontalBars:NO];
barPlot.baseValue = CPTDecimalFromString(@"0");
barPlot.dataSource = self;
barPlot.barOffset = CPTDecimalFromFloat(-0.6f);
barPlot.barWidth = CPTDecimalFromFloat(.5);
barPlot.delegate = self;
barPlot.identifier = (NSString *)[identifiers objectAtIndex:0];
[barChart addPlot:barPlot toPlotSpace:plotSpace];

NSLog(@"barPlot.identifier: %@", barPlot.identifier);

// Second bar plot
barPlot = [CPTBarPlot tubularBarPlotWithColor:[CPTColor blueColor] horizontalBars:NO];
barPlot.dataSource = self;
barPlot.barOffset = CPTDecimalFromFloat(-0.4f);
barPlot.barWidth = CPTDecimalFromFloat(.5);
barPlot.baseValue = CPTDecimalFromString(@"0");
barPlot.identifier = (NSString *)[identifiers objectAtIndex:1];
barPlot.delegate = self;
[barChart addPlot:barPlot toPlotSpace:plotSpace];

NSLog(@"barPlot.identifier: %@", barPlot.identifier);

//third bar plot
barPlot = [CPTBarPlot tubularBarPlotWithColor:[CPTColor redColor] horizontalBars:NO];
barPlot.dataSource = self;
barPlot.barOffset = CPTDecimalFromFloat(-0.2f);
barPlot.barWidth = CPTDecimalFromFloat(.5);
barPlot.baseValue = CPTDecimalFromString(@"0");
barPlot.identifier = (NSString *)[identifiers objectAtIndex:2];
barPlot.delegate = self;
[barChart addPlot:barPlot toPlotSpace:plotSpace];

NSLog(@"barPlot.identifier: %@", barPlot.identifier);

// Add legend
CPTLegend *theLegend = [CPTLegend legendWithGraph:barChart];
theLegend.numberOfColumns = 3;
theLegend.numberOfRows = 1;
theLegend.fill = [CPTFill fillWithColor:[CPTColor whiteColor]];
theLegend.borderLineStyle = [CPTLineStyle lineStyle];
theLegend.cornerRadius = 5.0;

barChart.legend = theLegend;
barChart.legendAnchor = CPTRectAnchorTopRight;
barChart.legendDisplacement = CGPointMake(-10.0f, -20.0f);

Thanks for the help!

Answer 1

Make sure neither of the following methods are implemented in your plot datasource:

-legendTitleForBarPlot:recordIndex:
-barFillForBarPlot:recordIndex:

If either of these methods exist, the plot creates a legend entry for each bar rather than using a single legend entry for the whole plot.