﻿ Linear Trendline Filter | JavaScript Chart Documentation
 SciChart.js JavaScript 2D Charts API > 2D Chart Types > Data Filters (Transforms) API > Linear Trendline Filter
Linear Trendline Filter

The Linear Trend filter calculates a straight line best-fit for your DataSeries. This can then be plotted as a line series on the chart.

## Applying a Linear Trendline to Chart Data

To calculate a Linear Trendline use the following code.

```import { SciChartSurface } from 'scichart/Charting/Visuals/SciChartSurface';
import { NumericAxis } from 'scichart/Charting/Visuals/Axis/NumericAxis';
import { XyDataSeries } from 'scichart/Charting/Model/XyDataSeries';
import { FastLineRenderableSeries } from 'scichart/Charting/Visuals/RenderableSeries/FastLineRenderableSeries';
import { XyScatterRenderableSeries } from 'scichart/Charting/Visuals/RenderableSeries/XyScatterRenderableSeries';
import { NumberRange } from 'scichart/Core/NumberRange';
import { XyLinearTrendFilter } from 'scichart/Charting/Model/Filters/XyLinearTrendFilter';
...
const { sciChartSurface, wasmContext } = await SciChartSurface.create('scichart-div-id-2');
sciChartSurface.xAxes.add(new NumericAxis(wasmContext, { growBy: new NumberRange(0.1, 0.1) }));
sciChartSurface.yAxes.add(new NumericAxis(wasmContext, { growBy: new NumberRange(0.1, 0.1) }));
// Original Data
const dataSeries = new XyDataSeries(wasmContext, {
xValues: [1, 2, 3, 4, 5],
yValues: [1, 3, 2, 4, 6],
});
const originalLine = new XyScatterRenderableSeries(wasmContext, { dataSeries });
// Create the filter, passing in the original series
const linearTrendFilter = new XyLinearTrendFilter(dataSeries);
const filteredLine = new FastLineRenderableSeries(wasmContext, { dataSeries: linearTrendFilter, stroke: "#cc6600" });
```

This results in the following output:

## Accessing Trendline Properties

The XyLinearTrendFilter has properties for slope, intercept and correlation which you can use to access the parameters of the trend line.

For example you could display them using an annotation like this:

```import { TextAnnotation } from "scichart/Charting/Visuals/Annotations/TextAnnotation";
import { EHorizontalAnchorPoint, EVerticalAnchorPoint } from "scichart/types/AnchorPoint";
const textAnnotation = new TextAnnotation({
x1: 1,
y1: 5,
fontSize: 20,
text: `Slope: \${linearTrendFilter.slope}, y-intercept: \${linearTrendFilter.intercept}, correlation: \${linearTrendFilter.correlation.toFixed(3)}`
});
```

## Specifying the Input Field

The XyLinearTrendFilter produces an XyDataSeries, but it can accept any series type as input. The options includes a field property of type EDataSeriesField, which determines which field on the original series will be the input.

This example takes a OHLC Series as input and plots separate trendlines for the High and Low values:

```import { OhlcDataSeries } from 'scichart/Charting/Model/OhlcDataSeries';
import { FastLineRenderableSeries } from 'scichart/Charting/Visuals/RenderableSeries/FastLineRenderableSeries';
import { FastCandlestickRenderableSeries } from 'scichart/Charting/Visuals/RenderableSeries/FastCandlestickRenderableSeries';
import { XyLinearTrendFilter } from 'scichart/Charting/Model/Filters/XyLinearTrendFilter';
import { EDataSeriesField } from "scichart/Charting/Model/Filters/XyFilterBase";
...
// Original Data
const dataSeries = new OhlcDataSeries(wasmContext, {
xValues: [1, 2, 3, 4, 5],
openValues: [1, 3, 2, 4, 6],
highValues: [5, 4, 7, 6.5, 8],
lowValues: [0.5, 2, 1.5, 2.5, 4],
closeValues: [3, 2.5, 5, 3, 5],
});
const rsCandles = new FastCandlestickRenderableSeries(wasmContext, { dataSeries });
// Create the filters, passing in the original series and specifying the input field
const linearTrendHigh = new XyLinearTrendFilter(dataSeries, { field: EDataSeriesField.High });
const linearTrendLow = new XyLinearTrendFilter(dataSeries, { field: EDataSeriesField.Low });
const rsHigh = new FastLineRenderableSeries(wasmContext, { dataSeries: linearTrendHigh, stroke: "#ddff33", strokeThickness: 3 });
const rsLow = new FastLineRenderableSeries(wasmContext, { dataSeries: linearTrendLow, stroke: "#ff5599", strokeThickness: 3 });