# [Libreoffice-qa] Trendline equation

Stefan Weigel stefan.weigel at bildungskreis.org
Sat Feb 1 22:02:04 CET 2014

```Hi again,

Am 31.01.2014 12:35, schrieb Laurent BP:

> Stefan Weigel wrote
>> > 1. Enter Data A1=11, A2=13, A3=12, A4=14, A5=16, A6=15
>> > 2. Select A1:A6
>> > 3. 4. Create a Line chart
>> > 4. Insert linear trendline and show equation
>> >
>> > --> Equation does make sense.

> If you do not specify X-values/categories, what sense can you give in the
> equation for 'x'?
> From my point of view, equation is useful if you need to extrapolate or
> interpolate values. What else?

Sure.

A1= Oct | B1= 1100 US\$
A2= Nov | B2= 1300 US\$
A3= Dec | B3= 1200 US\$
A4= Jan | B4= 1400 US\$
A5= Feb | B5= 1600 US\$
A6= Mar | B6= 1500 US\$

Create a Column chart. Insert formula.
Formula reads: f(x) = 88,57x + 1040

You can use the formula displayed in a Line chart or Column chart in
order to extrapolate the row to the following months. X would be the
number of the month, counting from October = 1.

Extrapolate July: f(x=10) = 1926

No matter if you do specify X-values or categories or not. Anyway,
there are lots of cases, where the formula is usefull in a regular
chart that does not need to be a XY chart.

Stefan.

--
LibreOffice - Die Freiheit nehm' ich mir!
```