R code from class on 1/25.  Here is the Recife data and yield data. 

R code from class on 2/1.

R code from class on 2/15.

R code from class on 2/22.  Here is the data for the second example.

R code from class on 2/29.

R code from class on 3/21.

R code from class on 3/28.

R code from class on 4/4.

R code from class on 4/11.

R code from class on 4/18.

R code from class on 4/25.