Full_Name: Dave DeBarr Version: 2.1.1 OS: Windows XP Professional Submission from: (NULL) (68.227.217.198) When issuing the command "acf(ts.union(mdeaths, fdeaths))", the plot.acf() function plots the negative lags of the autocorrelation values for mdeaths and fdeaths in the lower left-hand corner of the graphics window, but plot.acf() labels this graph as "fdeaths & mdeaths" (instead of "mdeaths & fdeaths"). The order of the variables does matter for the autocorrelation function.