I am not able set fixed bar width core plot bar graph

Question

Implemented bar graph using core plot calling objective-c methods in Swift language,I am able plot the graph but bars have different width in size, first and last one are different and the middle one are same

@IBAction func onBarGraphBtnPressed(_ sender: Any) {
        
        let a = chart!
        a.graphType = kBar
        a.clearData()
        let symbol = LCPlotSymbol()
        symbol.color = UIColor.yellow

        let plot1 = LCPlot()
        plot1.data = randomData(for: 3)
       // plot1.lineColor = UIColor.yellow
        plot1.fillColor = UIColor(red: 0.98, green: 0.59, blue: 0.07, alpha: 1.00)
        a.add(plot1)
        
        let ys: [LCAxisLabel] = [0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5].map {
            let label = LCAxisLabel()
            label.index = CGFloat($0)
            label.text = "$\($0)k"
            return label
        }
        chart.resetYAxisLabels(ys)
        var index = 0
        let xs: [LCAxisLabel] = ["Jan", "Feb", "Mar", "Apr","May", "Jun", "Jul", "Aug", "Sep","Oct", "Nov","Dec"].map {
            let x = LCAxisLabel()
            x.index = CGFloat(index)
            x.text = $0
            index = index + 1
            return x
        }
        
        chart.resetXAxisLabels(xs)
        chart.configureXAxisGridLine(nil)
        //chart.configureYAxisGridLine(nil)
        let gridLineStyle = LCLineStyle()
        gridLineStyle.lineWidth = 0.3
        gridLineStyle.lineColor = UIColor.gray
        chart.configureYAxisGridLine(gridLineStyle)
        
        chart.frame = self.view.bounds
        
        chart.padding = 0
        a.render()
    }