In a linear series, the step value, or the difference between the first and next value in the series, is added to the starting value and then added to each subsequent value.
| Initial selection | Extended linear series |
|---|---|
| 1, 2 | 3, 4, 5 |
| 1, 3 | 5, 7, 9 |
| 100, 95 | 90, 85 |
Filling in values for an exponential growth trend
In a growth series, the starting value is multiplied by the step value to get the next value in the series. The resulting product and each subsequent product is then multiplied by the step value.
| Initial selection | Extended growth series |
|---|---|
| 1, 2 | 4, 8, 16 |
| 1, 3 | 9, 27, 81 |
| 2, 3 | 4.5, 6.75, 10.125 |
Filling in values manually
When you use the Series command, you can manually control how a linear or growth trend is created and use the keyboard to fill in values.
- In a linear series, the starting values are applied to the least-squares algorithm (y=mx+b) to generate the series.
- In a growth series, the starting values are applied to the exponential curve algorithm (y=b*m^x) to generate the series.
In either case, the step value is ignored. The series created is equivalent to the values returned by the TREND function or GROWTH function.
Calculating trends by adding a trendline to a chart
You can create a trendline in a chart without creating the data for the trendline.
Projecting values with a worksheet function
The FORECAST function predicts new values based on a least-squares linear regression of a range of known data or known x-arrays and y-arrays. For example, given corporate earnings for each of the previous six quarters, the FORECAST function returns earnings expected for the next two quarters.
Using the TREND or GROWTH functions
The TREND function and GROWTH function can extrapolate future y-values that extend a straight line or exponential curve that best describes the existing data. They can also return only the y-values based on known x-values for the best-fit line or curve. To plot a line or curve that describes existing data, use the existing x-values and y-values returned by the TREND or GROWTH function.
Using the LINEST or LOGEST function
You can use the LINEST or LOGEST function to calculate a straight line or exponential curve from existing data. The LINEST function and LOGEST function return various regression statistics, including the slope and intercept of the best-fit line.
Performing regression analysis with the Analysis ToolPak add-in
When you need to perform more complicated regression analysis