I am analyzing growth over time for 5 different cultivated forms (cultivars) of maize. Graphing the data reveals a clear linear pattern for all the cultivars in the time interval I am interested in. Multiple linear regression with categorical (5 cultivars) and continuous (7 time points) explanatory variables appears to be one way to approach this problem, but I am having trouble with the coding in SAS 9.3. I'd like to compare slopes and intercepts between all the genotypes. I should add that new (independent) organ samples were taken at each time point (e.i. I did not measure the same plant organ at each time point).
So far, I've read the
proc reg manual, and some very useful information at http://www.ats.ucla.edu/stat/sas/webbooks/reg/Chapter7/sasreg7.htm.
Nonetheless, I haven't found a straightforward example on how to approach this problem.