## Introduction

Someone asked me the other day how I use the forecast functions in Excel. As I started thinking about it, I realised just how many FORECAST functions there are in*Office365 Excel*: here they all are:

FORECAST |

FORECST.LINEAR |

FORECAST.ETS |

FORECAST.ETS.CONFINT LOWER |

FORECAST.ETS.CONFINT UPPER |

FORECAST.ETS.SEASONALITY |

FORECAST.ETS.STAT |

### FORECAST Syntax

- =FORECAST(x, known_ys,known_xs)
- =FORECAST.LINEAR(x, known_ys,known_xs)
- =FORECAST.ETS(forecast_date,values,timeline,[seasonality],[data_completion],[aggregation])
- =FORECAST.ETS.CONFINT(target_date,values,timeline,[confidence_level],[seasonality],[data_completion],[aggregation])
- =FORECAST.ETS.SEASONALITY(values,timeline,[data_completion],[aggregation])
- =FORECAST.ETS.STAT(values,timeline,statistic_type,[seasonality],[data_completion],[aggregation]) …

**Confidence Interval**function can be used to find both the

**lower**and

**upper**limits: see the example below for ideas in action. The

**to choose from are:**

*Statistic Types***Alpha parameter of ETS algorithm**Returns the base value parameter: a higher value gives more weight to recent data points.**Beta parameter of ETS algorithm**Returns the trend value parameter: a higher value gives more weight to the recent trend.**Gamma parameter of ETS algorithm**Returns the seasonality value parameter: a higher value gives more weight to the recent seasonal period.**MASE metric**Returns the mean absolute scaled error metric: a measure of the accuracy of forecasts.**SMAPE metric**Returns the symmetric mean absolute percentage error metric: an accuracy measure based on percentage errors.**MAE metric**Returns the symmetric mean absolute percentage error metric: an accuracy measure based on percentage errors.**RMSE metric**Returns the root mean squared error metric: a measure of the differences between predicted and observed values.**Step size detected**Returns the step size detected in the historical timeline.

**Forecast Sheet**: compare the results with the .ETS, .CONFINT, .ETS.STAT functions I used: