Linear and exponential trendlines.(see the doc of Google)

Data format

Each row in the table represents a set of data points with the same x-axis location. See details

Column	Type	Description
0	string (discrete) or number, date, datetime, or timeofday (continuous)	X-axis group labels (discrete) or X-axis values (continuous)
1	Number	Line 1 values
N	Number	Line N values

Chart options

Each option is separated by a '|' or '!' (for Mediawiki).

Name	Default	Description
width	100%	Chart width
height		Chart height
trendlines.0.type	linear	Google Charts supports three types of trendlines: linear, polynomial, and exponential.
Others...		You can use the configuration options of Google. See the doc

Linear trendline (by default)

Without options

Exponential trendlines

Example with options : "trendlines.0.type=exponential|trendlines.0.visibleInLegend=true|trendlines.0.color=red"