# Chart2/TrendLines

From Apache OpenOffice Wiki

## Contents

## Add polynomial regression type

- Different types of regression lines are already offered: linear regression, exponential regression. But a polynomial regression curve is still missing. A macro on this site offers a workaround (french only):
- http://oooconv.free.fr/fitoo/fitoo_fr.html
- covered in http://www.openoffice.org/issues/show_bug.cgi?id=20819

## Allow more than one regression line for one series

## Extrapolating of trend lines

- Trend lines should also allow extrapolating. If data ranges from 1 to 5 but that x axes range from -2 to 10, then the trend line should display from -2 to +10.
- In Excel, the setting is called forward forecast and backward forecast.
- covered in http://www.openoffice.org/issues/show_bug.cgi?id=5085

## Mean value for X and center of gravity

- Get the mean value not only for Y but also for X. A special symbol could mark the intersection point (the center of gravity).
- covered in http://www.openoffice.org/issues/show_bug.cgi?id=64816

## Error bar for X

- Error bar for X added to the existent Y one
- covered in http://www.openoffice.org/issues/show_bug.cgi?id=42946