# Trend and Forecasting

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The Trend and Forecasting function calculates a regression line or line of best fit. When applied to a time series, it can forecast future values.

This function can be used with a measure and date/time values, or with two measures where each is typically plotted along a separate chart axis.

There are four regression functions available:

## 1. Syntax

Trend and Forecasting:

```TRENDFORE(d0,d1,s0,s1,s2)
```

Upper Band Error:

```TRENDFOREUPPER(d0,d1,s0,s1,s2)
```

Lower Band Error:

```TRENDFORELOWER(d0,d1,s0,s1,s2)
```

Axis:

`TRENDFOREAXIS(d0,d1,s0,s1,s2)`

## 2. Input

The Trend and Forecasting functions require the following input series:

• d0 - Trend Axis values - The set of values on the trending axis (e.g. datetime axis).
• d1 - Input data values - The set of historical data values to be used in the Trend and Forecasting formula.

## 3. Parameters

• s0 - Regression Type - The type of regression function used by the Trend and Forecasting formula. Available choices include:
• 0 - Linear (default)
• 1 - Exponential
• 2 - Logarithmic
• 3 - Power
• s1 - Regression Degree - The degree used by the regression function in calculating the Trend and Forecasting formula. Default value is 2.
• s2 - Forecasting Period - The length of the forecasted data series as returned by the Trend and Forecasting formula. Available choices include:
• 0 - No Forecast
• 1 - Tenth Input
• 2 - Quarter Input
• 3 - Half Input (default)
• 4 - Full Input

## 4. Output

The Trend and Forecasting functions generate the following outputs:

• Trend and Forecasting - The Trend and Forecasting result set.
• Upper Band Error - The upper error boundary based on standard deviation and the forecasting error.
• Lower Band Error - The lower error boundary based on standard deviation and the forecasting error.

## 5. Examples

### 5.1. Trend and forecast on a time series

This example adds a trend line including a forecast to a line chart.

With a measure and time dimension hierarchy displayed in a chart like the following:

You can quickly add a trend line by choosing Re-Visualize in the toolbar, then Add Trend Line.

This adds a formula measure that uses the TRENDFORE function with the default forecasting settings, visualized as a new line series.

You can now edit the formula if you choose to.

### 5.2. Linear regression on scatter plot

This example shows how to add a regression line, or line of best fit to a scatter plot.

With a scatter plot chart displaying two measures grouped by one or more hierarchies:

You can quickly add a trend line by choosing Re-Visualize in the toolbar, then Add Trend Line.

This adds a formula measure that uses the TRENDFORE function, visualized as a new line series.

You can now edit the formula if you choose to.

## 6. Notes

• The forecast will only go ahead in time as far as the time dimension's end date.

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