There are a number of ways to check whether time series data is stationary or non-stationary:
- Through visualizations: You can review a time series graph for obvious indication of trends or seasonality.
- Through statistical summaries: You can review the statistical summaries of your data significant differences. For example, you can partition your time series data and compare the mean and variance of each group.
- Through statistical tests: You can use statistical tests such as the Augmented Dickey-Fuller Test to check if stationarity expectations have been met or violated.