The ability to easily add a trend line for charts, should include the following options:
Must have
Linear
Moving Average
Nice to have
Polynomial
Exponential
Power
Logarithmic
Compound Annual Growth Rate (CAGR)
Index
Ideal
Custom expression driven trendlines
Options
Configurable confidence interval overlay (e.g. 95% confidence zone around regression line)
Configuration parameters for regressions (e.g. periods in moving average)
Configurable forward projection (i.e. forecast)
Ability to display line equation
The usual colour options etc