I have a 4-set of time series data and each dataset has a response and its recorded date as a decimal year. For instance, there is a dataset from 2002 to 2013 having 200 data points, each data point has recorded on a distinct decimal year. I obtained slope for each data-set as my predictor is 'decimal year'. Hence, I obtained 4 different slopes for 4 datasets and I had to plot in a different graph as all these time series datasets were recorded on a distinct decimal year. My question is how can I compare these four slopes obtained from each data set as they are statistically equal or not. I went through various methods: ANOVA, t-tests, ANCOVA etc., but never got a clear idea. I am doing this analysis in r.