# periodic time series

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## periodic time series

 Hi all, A beginner's question: I have to analyse univariate, strongly periodic data collected every hour for a period of 1 week and I need to compare 5 different groups for significant differences between them. Is there a better way to do this in R, other than pairwise t-tests of summary statistics? Thanks in advance, Andy
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## Re: periodic time series

 Hi Andy, If you could provide a sample data set, it would help others to give a solution. I suggest look at the data and select a model, then anova. Take group as one variable, record time (1 to 24 ) as the second variable and the week day (Monday to Friday) as the third variable. Then test the interaction between three variables at first. I hope the following code helps. df <- data.frame(value = rnorm(24*5*5),         group = rep(1:5,5*24),         time = rep(1:24,each=5),         day = rep(c("M","T","W","R","F"),each=24)) anova(lm(value ~ group*time*day,data=df),lm(value ~ group*time*day-group:time:day,data=df))