Hi everyone,

I am currently trying to plot a stacked bar chart. However the width of the bars are not equal. I am plotting 5 bars with each bar stacked with two. I have attached an image of the bar chart. Only the first and last bar are not in equal size as the rest of the bars. I have also attached the portion of code which generates the barchart, below. Please guide me on how to solve this issue.

barchart.jpg

Qt Code: 
  1. BarChart::BarChart(QWidget *parent)
  2.     : QwtPlot(parent)
  3. {
  4.     setAutoFillBackground(true);
  5.     setPalette(Qt::white);
  6.     canvas()->setPalette(QColor ("Black")); //background color
  7.  
  8.     barChart = new QwtPlotMultiBarChart;
  9.     barChart->setLayoutPolicy(QwtPlotMultiBarChart::AutoAdjustSamples);                                                            
  10.     barChart->setSpacing(20);      
  11.     barChart->setMargin(20);     
  12.     barChart->setStyle(QwtPlotMultiBarChart::Stacked);                               
  13.     barChart->attach(this); 
  14.  
  15.  
  16.     for(int i = 0; i < 2; ++i)
  17.     {
  18.         QwtColumnSymbol *symbol = new QwtColumnSymbol(QwtColumnSymbol::Box);
  19.         QPalette barColor = (i == 0) ? Qt::green : Qt::red ;
  20.         symbol->setPalette(barColor);
  21.         symbol->setFrameStyle(QwtColumnSymbol::Raised);
  22.         symbol->setLineWidth(1);    
  23.         barChart->setSymbol(i, symbol);
  24.     }
  25.  
  26.     QVector<QVector<double> > newBarChartData;
  27.     for(int i = 0; i < 5; i++)
  28.     {
  29.         num = rand() % 100;
  30.         QVector<double> values;
  31.         values.push_back(num);
  32.         values.push_back(100-num);
  33.  
  34.         newBarChartData.push_back(values);
  35.     }
  36.     barChart->setSamples(newData);
  37.  
  38.     QwtPlot::Axis yAxis = QwtPlot::yLeft,
  39.                   xAxis = QwtPlot::xBottom;
  40.     setAxisScale(yAxis, 0, 100, 20);
  41.     setAxisAutoScale(xAxis);
  42.     enableAxis(yAxis, true);
  43.     enableAxis(xAxis, false);
  44.  
  45.     QwtScaleDraw *yAxis_scaleDraw = axisScaleDraw(yAxis);
  46.     yAxis_scaleDraw->enableComponent(QwtScaleDraw::Backbone, false);
  47.     yAxis_scaleDraw->enableComponent(QwtScaleDraw::Ticks, false);
  48.  
  49.     QwtScaleDraw *xAxis_scaleDraw = axisScaleDraw(xAxis);
  50.     xAxis_scaleDraw->enableComponent(QwtScaleDraw::Backbone, false);
  51.     xAxis_scaleDraw->enableComponent(QwtScaleDraw::Ticks, false);
  52.  
  53.     plotLayout()->setCanvasMargin(0); 
  54.     updateCanvasMargins();
  55.     replot();
  56. }
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