# Determining Seasonality nature of a time series i.e additive or multiplicative

I have 4 years of data starting from 2014-Jan to 2017-Dec, I am trying to extract seasonality component from that series, to do this I am using decompose function in R, one of the parameters to decompose function is type of time series, but I am not able to visually tell if it si additive or multiplicative

What happens if I don't pass any parameter to decompose function, in the help function there is no default parameter mentioned

I decomposed the ts by trying both additive and multiplicative seasonality type, but don't see much variation

• The default for stats::decompose is additive, because it is the first in the list in the call in the "usage" section of the help page. This is a convention in R, used to enforce "enum"-like behavior (see match.arg). – Chris Haug Apr 11 '18 at 13:59
• @ChrisHaug , oh, what do you think about the above series, how can I check for the nature of seasonality ? – av abhishiek Apr 11 '18 at 14:11