Sorry of a similar question has been asked before but I did not get my answer.
I have some TV viewership (which I can not provide, I am sorry) that I am pretty sure has 3 periodicities: daily, weekly and yearly. I know this because I can see that in the graphs when I plot the viewership every half an hour throughout the year.
This can be very clearly seen in the picture below: there are peaks at prime time every day, there is a dip every weekend (more drop on Sundays, there are outliers for different events when the viewership falls but we are not interested in that right now). When plotted for the whole year, I can see there is a fast fall in April-May and a slow rise towards the year end.
However, I want to confirm these numbers (1, 7, 366) for the
msts function in R are correct.
ts1 <- ts(channel_views$Impressions) acf(ts1, lag.max = 1000)
When I plot The ACF, I can see peaks at multiples of 7 indicating weekly seasonality. But how do I know from ACF there are more seasonalities in the data?