KoolReport 3.25.4:

The result of my ScatterChart (body size vs. body weight) looks like this:

Which kind of functionality do I need to put into this to have something like the orange line (being a trendline or trend indicator)?

I have already read the forum threads #708 and #709, but is "trendlines" the right way to do it?

Isn't there a way to define the trendline as the difference between the min and the max value of a database record set such as

[...]
),
"options"=>array(
    "vAxis"=>array(
        "title"=>"Körpergrösse",
    ),
    "hAxis"=>array(
        "title"=>"Körpergewicht"
    ),
    "trendlines"=>array(
        array_sum(min($row['weightrange']))=>array_sum(max($row['weightrange']))
	)
)
[...]

working with average values here (weight and body size are numerical values)?