Created attachment 124601 [details]
Libreoffice can add trend line equation in to the plot automatically.

In LibreOffice, there are add trend line equation option. This trend line is the fit curve equation that is display as text on the plot.

Currently, the only way to do it on labplot is to write out the trend line equation manually, but it take more time and several jump through hoops, the equation also have to be edit when the line equation change.

So I would like to propose a feature that add fit curve equation to the plot and update itself when the equation change.

The equation is usually written with y-axis as f(x) and x-axis as x, 
f(x) = 5x + 3

labplot-kf5-2.7.0-1.3

Operating System: openSUSE Tumbleweed 20191207
KDE Plasma Version: 5.17.3
KDE Frameworks Version: 5.64.0
Qt Version: 5.13.1
Kernel Version: 5.3.12-1-default
OS Type: 64-bit
Processors: 8 × Intel® Core™ i7-3770 CPU @ 3.40GHz
Memory: 7.5 GiB of RAM