Home / Statistical Tools / Analysis Tools / Time Series / Trend Analysis
Trend Analysis¶
Fit a straight or curved trend to a series over time and, if you want, extend it into the future.
Where to find it
QXL Stat Tools → Analysis Tools → Time Series → Trend Analysis
Worked example
The Quick Start walkthrough builds this analysis step by step from sample data you can copy straight into Excel, and states every number it produces.
All six Time Series walkthroughs are listed on the How-To page.
What it does¶
Trend Analysis fits your data against the observation index (1, 2, 3, ...) with either a linear or a quadratic model, plots the actual and fitted values, and reports the fitted equation and forecast accuracy measures. Optional forecasts extend the fitted trend beyond the data.
Options¶
The dialog is Time Series Smoothing, with a Data tab and an Options tab.
Data tab
- Excel / GroupBy: analyze flat Excel columns, or split by one or more GroupBy columns (each group gets its own analysis)
- Data Columns: one or more numeric columns; each produces its own analysis
- Overlay Datasets on a Single Chart: combine the selected series into one chart
Options tab (Trend Analysis Options)
- Linear / Quadratic: the trend model. Linear is the default; Quadratic adds a curvature term.
- Number of Forecasts: how many periods to extend the trend past the data. Default 0 (no forecast); must be 0 or more.
Output¶
A worksheet named Trend ... containing:
- A line chart with the Actual, Fitted, and (when forecasting) Forecast series over the observation Index
- A data table with Index, Actual, Predicted, Error columns
- An Accuracy Measures table with MAPE, MAD, and MSD
- An Equation table showing the fitted trend, \(y = a + bx\) (linear) or \(y = a + bx + cx^2\) (quadratic)