using simple R lines, I have plots of decomposition of a time series.
DCB = decompose(ts_series, "additive") plot(as.ts(DCB$seasonal)) plot(as.ts(DCB$trend)) plot(as.ts(DCB$random)) plot(DCB)
Not obvious if it's additive or multiplicative so I did both. the outputs are similar.
The "observed", which is the plot of the numbers itself, shows a relatively flat movement. However the trend decomposed, shows an obvious downward trend.
Why are they so different (the Observed vs the Trend)? and the Trend is missing it's beginning and ending parts? Thank you.