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Spline Charts
Spline charts are a specialized form of line charts that display smooth curves through the different data points.
In this section, you will be introduced to the:
- 
    
Basics of spline charts
 - 
    
Types of spline charts
 
Basics of Spline Charts
Spline charts integrate all the characteristics of a conventional line chart except for the fact that unlike line charts, which connect data points with straight lines, spline charts draw a fitted curved line to join the data points.
Spline charts can be used for plotting data that requires the usage of curve-fitting e.g. an impulse-response chart, a product life cycle chart, etc. It is also significantly used in designing Pareto charts.
Types
FusionCharts Suite XT includes four types of spline charts:
- 
    
Single-series spline 2D chart
 - 
    
Multi-series spline 2D chart
 - 
    
Single-series spline area 2D chart
 - 
    
Multi-series spline area 2D chart
 
Single-series Spline 2D Chart
A single-series spline 2D chart draws a single fitted curve through the data points.
A simple single-series spline 2D chart looks like this:
The data structure needed to render a single-series spline 2D chart is given below:
{
    "chart": {
        "caption": "Total footfall in Bakersfield Central",
        "subCaption": "Last week",
        "xAxisName": "Day",
        "yAxisName": "No. of Footfalls",
        "lineThickness": "2",
        "paletteColors": "#008ee4,#6baa01",
        "baseFontColor": "#333333",
        "baseFont": "Helvetica Neue,Arial",
        "captionFontSize": "14",
        "subcaptionFontSize": "14",
        "subcaptionFontBold": "0",
        "showBorder": "0",
        "showValues": "0",
        "bgColor": "#ffffff",
        "showShadow": "0",
        "canvasBgColor": "#ffffff",
        "canvasBorderAlpha": "0",
        "divlineAlpha": "100",
        "divlineColor": "#999999",
        "divlineThickness": "1",
        "divLineIsDashed": "1",
        "divLineDashLen": "1",
        "divLineGapLen": "1",
        "showXAxisLine": "1",
        "xAxisLineThickness": "1",
        "xAxisLineColor": "#999999",
        "showAlternateHGridColor": "0"
    },
    "data": [
        {
            "label": "Mon",
            "value": "15123"
        },
        {
            "label": "Tue",
            "value": "14233"
        },
        {
            "label": "Wed",
            "value": "25507"
        },
        {
            "vline": "true",
            "lineposition": "0",
            "color": "#6baa01",
            "labelHAlign": "left",
            "label": "National holiday"
        },
        {
            "label": "Thu",
            "value": "9110"
        },
        {
            "label": "Fri",
            "value": "15529"
        },
        {
            "label": "Sat",
            "value": "20803"
        },
        {
            "label": "Sun",
            "value": "19202"
        }
    ]
}Multi-series Spline 2D Chart
A simple multi-series spline 2D chart looks like this:
To render a multi-series spline chart:
- 
    
Set the
typeattribute tomsspline. - 
    
Use the
seriesnameattribute and thedataobject, which belong to thedatasetobject, to specify multiple datasets. 
Multi-series Spline Area 2D Chart
A multi-series spline area 2D chart is nothing but a conventional area with a smoothened curve drawn through the data points in the series. It allows you to plot data for multiple data sets.
A simple multi-series spline area 2D chart looks like this:
The data structure needed to render a multi-series spline area 2D chart is given below:
{
    "chart": {
        "caption": "Number of Footfalls Last Week",
        "subCaption": "Garden Groove harbour vs Crompton-Rancho Dom",
        "xAxisName": "Day",
        "yAxisName": "No. of Footfalls",
        "captionFontSize": "14",
        "subcaptionFontSize": "14",
        "baseFontColor": "#333333",
        "baseFont": "Helvetica Neue,Arial",
        "subcaptionFontBold": "0",
        "paletteColors": "#6baa01,#008ee4",
        "usePlotGradientColor": "0",
        "bgColor": "#ffffff",
        "showBorder": "0",
        "showPlotBorder": "0",
        "showValues": "0",
        "showShadow": "0",
        "showAlternateHGridColor": "0",
        "showCanvasBorder": "0",
        "showXAxisLine": "1",
        "xAxisLineThickness": "1",
        "xAxisLineColor": "#999999",
        "canvasBgColor": "#ffffff",
        "divlineAlpha": "100",
        "divlineColor": "#999999",
        "divlineThickness": "1",
        "divLineIsDashed": "1",
        "divLineDashLen": "1",
        "divLineGapLen": "1",
        "legendBorderAlpha": "0",
        "legendShadow": "0",
        "toolTipColor": "#ffffff",
        "toolTipBorderThickness": "0",
        "toolTipBgColor": "#000000",
        "toolTipBgAlpha": "80",
        "toolTipBorderRadius": "2",
        "toolTipPadding": "5"
    },
    "categories": [
        {
            "category": [
                {
                    "label": "Mon"
                },
                {
                    "label": "Tue"
                },
                {
                    "label": "Wed"
                },
                {
                    "vline": "true",
                    "lineposition": "0",
                    "color": "#6baa01",
                    "labelHAlign": "right",
                    "labelPosition": "0",
                    "label": "National holiday"
                },
                {
                    "label": "Thu"
                },
                {
                    "label": "Fri"
                },
                {
                    "label": "Sat"
                },
                {
                    "label": "Sun"
                }
            ]
        }
    ],
    "dataset": [
        {
            "seriesname": "Garden Groove harbour",
            "data": [
                {
                    "value": "15123"
                },
                {
                    "value": "14233"
                },
                {
                    "value": "21507"
                },
                {
                    "value": "9110"
                },
                {
                    "value": "14829"
                },
                {
                    "value": "17503"
                },
                {
                    "value": "20202"
                }
            ]
        },
        {
            "seriesname": "Crompton-Rancho Dom",
            "data": [
                {
                    "value": "11400"
                },
                {
                    "value": "12800"
                },
                {
                    "value": "17800"
                },
                {
                    "value": "10400"
                },
                {
                    "value": "11800"
                },
                {
                    "value": "13100"
                },
                {
                    "value": "20800"
                }
            ]
        }
    ]
}Single-series Spline Area 2D Chart
A simple single-series spline area area 2D chart looks like this:
To render a single-series spline chart:
- Set the 
typeattribute tosplinearea. 
Spline and spline area charts do not support joining of empty data points in the chart. That means, if your chart does not contain data at a particular point, the data points cannot be connected to each other and will appear as a broken dataset.
There! You have now seen and understood the basics of spline charts and how the various types can be rendered.