type property
Specifies the intercept value of the trendlines.
Defaults to TrendlineType.linear.
Also refer TrendlineType.
Widget build(BuildContext context) {
  return SfCartesianChart(
    series: <CartesianSeries<ChartData,String>>[
      LineSeries<ChartData,String>(
        trendlines: <Trendline>[
          Trendline(type: TrendlineType.power)
        ]
      )
    ]
  );
}
Implementation
final TrendlineType type;