[R] Anova and covariable

john polo jpolo at mail.usf.edu
Tue Nov 24 22:49:12 CET 2009


   Dear R users,
   i want to use ANOVA with a small data set, here is an example of the data:

   Rich FireDe TimeS Area
      8      2     4      C
      9    2.5     7      C
      5    1.9     2      C
      7      3     4      C
      8    2.5     0      L
      2      4     3      L
      9    2.5     6      L
      9      3     6      L
     10    1.5     2      O
      3    3.5     9      O
      7      2     7      O
      5    2.5     4      O

   in a randomized block design, where the Areas are supposed to be the blocks,
   i want to test the null hypothesis for Rich and FireDe by itself or with
   TimeS. i would like to control for the Area, use it as a covariable i guess,
   but don't know how to with this:
   summary(lm(Rich~FireDe _ Area ))
   or
   summary(lm(Rich~FireDe _ TimeS _ Area))
   in the places i've looked, i've seen * and + used where i typed "_", but i
   wasn't sure if it was for a one-way or two-way Anova or a covariate.
   best regards,
   john polo
   G.R.A.
   OK State



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