how do I know that my time series data has a seasonal trend

I have a variable of Zenith Wet delay (represent the effect of water vapor on GPS signal) with time resolution 1-hour for three years, it's just a vector of one coulmn, and I want to use FFT to know if my data has a seasonal cycles or not, but I don't know how to put the Fs in it or how to choose the better sampling rate of my data.

any help please.

Thanks

Answer 1

[Vaibhav Tomar]

Please refer to the following link for an example on how to apply Sn×m seasonal filters to deseasonalize a time series (using a multiplicative decomposition). You can use the same technique for checking seasonality of your time data.

https://www.mathworks.com/help/econ/seasonal-adjustment-using-snxd7m-seasonal-filters.html

You can also refer here for more information and different ways to check seasonality:

https://www.mathworks.com/help/stats/examples/time-series-regression-of-airline-passenger-data.html