Ballardw, thanks for the quick response. The code I used was: input day pH; run; proc corr data=river kendall; var day; with pH; run; It produced two numbers for kendalls tau a -0.348 and then below it a 0.0070 We have 21 sites which were sampled every four weeks so we technically have 21 values for each sampling date. The code above was used for 1 site (30 observations) to test that it worked before being used for the entire data set.
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