In R, objects can be of different class such as vector, list, dataframe, ts, etc. When you load a dataset into R, it may not necessarily be a time series object. We can use the is.ts() function to test if the given object is a time series (ts) object or not.

Below we perform this test on all the objects we've created so far in this course.

> is.ts(msft_ts)
[1] TRUE
> is.ts(GDP_data)
[1] TRUE
> is.ts(sp_vector)
[1] FALSE
> is.ts(sp_ts)
[1] TRUE
>

As you can see, all objects return TRUE except sp_vector which is a vector.