Not clear what you're asking.

A trendline added to a series uses every point in the series in its
calculations.

If you want a trendline to use more than one series in its calculations,
you should create a series that uses all data from all series, and make
a trendline from this combined series.

- Jon
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Jon Peltier
Peltier Technical Services, Inc.
http://peltiertech.com/


On 4/5/2010 1:39 AM, shafierin wrote:
how can i add trendline or best fit line on a scatter plot which has
multiple set of data. for example, i had 3 set of data for 3 different
depth (0cm,15cm and 30cm) and i plot all three in a scatter plot. is it
posible if i want only a line for describe all three depth despite of
having a line for each color (3 line for 3 depth). or if i made all 3
depth together in one set of data and get a trendline from that
scatter, how i can differentiate which point is 0cm, 15cm and 30cm?